Lubricant management for an hvacr system

ABSTRACT

Systems and methods for lubricant management of a compressor in an HVACR system are disclosed. A heat transfer circuit can utilize a working fluid to provide heating or cooling includes a compressor for compressing the working fluid and a heat source configured to increase a suction temperature of the working fluid entering the compressor. One or more lubricant rheological properties in a compressor system based on measurements taken at or near a bearing cavity of the compressor are determinable. A lubricant reservoir can be in thermal communication with a discharge flow path of the compressor. An internal heat exchanger can be disposed within a compressor for improving viscosity of the lubricant to be cycled back into the compressor. A heater can be located on a fluid line between a lubricant separator and a lubricant inlet. Condenser fans can be controlled.

FIELD

This disclosure relates generally to a heating, ventilation, airconditioning, and refrigeration (HVACR) system. More specifically, thisdisclosure relates to lubricant management for a compressor in an HVACRsystem.

BACKGROUND

A heating, ventilation, air conditioning, and refrigeration (HVACR)system generally includes a compressor. Compressors, such as, but notlimited to, screw compressors and scroll compressors, utilize bearingsto support a rotating shaft. The bearings generally include a lubricantsystem. If the bearings are not properly lubricated, the bearings, andultimately the compressor, may fail prior to an expected lifetime of thebearing.

SUMMARY

This disclosure relates generally to a heating, ventilation, airconditioning, and refrigeration (HVACR) system. More specifically, thisdisclosure relates to lubricant management for a compressor in an HVACRsystem.

In an embodiment, a heat transfer circuit that utilizes a working fluidto provide heating or cooling includes a compressor for compressing theworking fluid and a heat source configured to increase a suctiontemperature of the working fluid entering the compressor.

In an embodiment, one or more lubricant rheological properties in acompressor system based on measurements taken at or near a bearingcavity of the compressor are determinable. The measurements may includea viscometer reading, a refractive index, a bearing cavity pressure anda bearing cavity temperature, or a bearing cavity temperature and asuction pressure of the compressor.

In an embodiment, a lubricant reservoir is in thermal communication witha discharge flow path of the compressor.

In an embodiment, an internal heat exchanger is disposed within acompressor for improving viscosity of the lubricant to be cycled backinto the compressor.

In an embodiment, compressor systems condition lubricant to allowoperation of the compressor under an increased variety of operatingconditions while maintaining bearing reliability. The compressor systemscan include a heater located on a fluid line between a lubricantseparator and a lubricant inlet.

In an embodiment, a method and system for controlling condenser fans ina heating, ventilation, and air conditioning (HVAC) system are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

References are made to the accompanying drawings that form a part ofthis disclosure, and which illustrate embodiments in which the systemsand methods described in this specification can be practiced.

FIG. 1 shows a system diagram of a compressor system, according to anembodiment.

FIG. 2 shows a system diagram of a compressor system, according to anembodiment.

FIG. 3 shows a flow chart of a method, according to an embodiment.

FIG. 4 is a front view of a bearing cover of a compressor according toan embodiment.

FIG. 5 is a section view of a compressor according to an embodiment.

FIG. 6 is a flow chart of a method of operating a compressor accordingto an embodiment.

FIG. 7 is a schematic view of an HVAC system that can employ fancontrol, according to one embodiment.

FIG. 8 illustrates a fan control system, according to one embodiment.

FIG. 9 is a flow chart of a method on fan control, according to oneembodiment.

FIG. 10 shows a relationship between the system pressure differentialand the ambient temperature, according to one embodiment

FIG. 11 is a schematic diagram of a heat transfer circuit, according toan embodiment.

FIG. 12 is a schematic diagram of a heat transfer circuit, according toan embodiment.

FIG. 13 is a schematic diagram of a heat transfer circuit, according toan embodiment.

FIG. 14 is a schematic diagram of a heat transfer circuit, according toan embodiment.

FIG. 15 is a diagram showing a flow of working fluid through anevaporator.

FIG. 16 is a block diagram of a method of operating a heat transfercircuit.

FIG. 17 is a schematic diagram of a refrigerant circuit, according to anembodiment.

FIG. 18 is a side sectional view of a compressor for a vapor compressionsystem (e.g., the refrigerant circuit of FIG. 17), according to anembodiment.

FIG. 19 is a side sectional view of a compressor for a vapor compressionsystem (e.g., the refrigerant circuit of FIG. 17), according to anembodiment.

FIG. 20 illustrates a schematic view of an embodiment of a refrigerationsystem.

FIG. 21 illustrates a schematic view of another embodiment of arefrigeration system.

FIG. 22 illustrates an example of a screw compressor, with which theembodiments as disclosed herein can be practiced.

FIG. 23 illustrates an example of an internal heat exchanger utilizingpassages drilled or casted in the bottom wall of the bearing housing ofa screw compressor, according to an embodiment.

FIG. 24 illustrates another example of an internal heat exchangerutilizing surface passages milled on an interface surface of the bearinghousing of a screw compressor, according to an embodiment.

FIG. 25 illustrates a circuit including a suction-line heat exchangeraccording to an embodiment.

FIG. 26A illustrates a perspective view of a suction-line heat exchangeraccording to an embodiment.

FIG. 26B illustrates a side view of a suction-line heat exchangeraccording to the embodiment shown in FIG. 26A.

FIG. 27 illustrates a heat exchanger baffle of a suction-line heatexchanger according to an embodiment.

DETAILED DESCRIPTION

This disclosure relates generally to a heating, ventilation, airconditioning, and refrigeration (HVACR) system. More specifically, thisdisclosure relates to lubricant management for a compressor in an HVACRsystem.

Environmental impacts of HVACR refrigerants are a growing concern. Forexample, since 2011, the European Union has been phasing outrefrigerants with a global warming potential (GWP) of more than, forexample, 150 in some refrigeration systems. Environmentally-suitableHVACR refrigerants, with suitable properties such as density, vaporpressure, heat of vaporization, and suitable chemical properties, whichsatisfy the requirements regarding safety and environment impacts, suchas the European Union standard discussed above, can be utilized forHVACR systems. The environmentally-suitable HVACR refrigerants arenonflammable or mildly flammable, non-ozone depleting, energy efficient,low in toxicity, compatible with materials of construction, and arechemically stable over the life of the equipment.

Current refrigerants, such as R134a or the like, may have relativelyhigher GWPs. For example, R134a has a GWP of 1,430. As a result,replacement refrigerants such as, but not limited to, R1234ze, R513A,and the like, are being implemented in HVACR systems.

In utilizing newer refrigerant compositions such as, but not limited to,R1234ze and R513A, various problems may arise as a result of thedifferent properties of the refrigerant compared to prior refrigerantssuch as R134a. In general, refrigerants with lower GWPs such as R1234ze,R513A, and the like may be carried over into the lubricant. In someinstances, the replacement refrigerants are relatively more likely todissolve into the lubricant than the current refrigerants, resulting ina higher concentration of refrigerant within the lubricant (e.g.,lubricant dilution).

As a result, portions of an operating map for a compressor of the HVACRsystem may suffer from higher lubricant dilution and limited bearingviscosity due to low discharge superheat. In some instances, theoccurrence of higher lubricant dilution and limited bearing viscositymay be more significant when the variable speed compressor operates atrelatively lower speeds. Higher lubricant dilution and limited bearingviscosity can result in, for example, a shortened lifetime for thebearings and ultimately compressor failures. In some instances,utilizing the R134A replacement refrigerants may require a replacementof the mechanical components (e.g., bearings or the like) in thecompressor.

In other instances, controlling a variable speed compressor to maximizeefficiency can also result in lubricant dilution problems, even whenutilizing the current refrigerants such as R134a.

In general, lubricants utilized with R134a replacement refrigerantssuffer the higher lubricant dilution problem. The lubricants can includeany suitable lubricant which is miscible with the selected replacementrefrigerant.

In general, higher lubricant dilution may occur when discharge superheatbecomes relatively low. For example, higher lubricant dilution can occurwhen the discharge superheat is below at or about 8° C.

Compressor System Having Isolated Heated Lubricant Flow (FIGS. 1-3)

This disclosure is directed to compressor systems where bearinglubricant flow is isolated and heated prior to being provided to thebearings, for example by a heater such as an electric heater or by heatexchange with heat scavenged from other compressor components.

Modern refrigerants may be more soluble in lubricants, and the dissolvedrefrigerant may compromise the effectiveness of the lubricant. Heat canbe used to drive out the dissolved refrigerant from the lubricant,conditioning the lubricant. By conditioning lubricant for use at thecompressor bearings, compressor systems according to embodimentsincrease the extent to which refrigerant can be separated fromlubricant, and thus improve lubricant quality (e.g. the mass fraction ofthe refrigerant dissolved in the lubricant). The improved lubricantquality allows operation at combinations of speed and capacity that maynot otherwise allow for sufficient lubrication of the bearings.Compressor systems according to embodiments thus can use a greaterportion of the operating map defined by combinations of compressor speedand capacity, and are capable of delivering improved efficiency byutilizing more of the operating map of the compressor that ordinarilymay not provide sufficient heat for effective separation of lubricantand refrigerant.

A compressor system embodiment includes a compressor having a suctionport, a discharge port, and a lubricant inlet. The compressor systemembodiment includes a lubricant storage. The compressor systemembodiment includes a fluid line, wherein the fluid line allows fluidcommunication between the lubricant storage and the lubricant inlet. Thecompressor system embodiment also includes a heat supply, thermallycoupled to the fluid line. The lubricant storage may be a lubricantsump, a lubricant tank, or the like. The lubricant sump may be part of alubricant separator located downstream of the discharge port of thecompressor.

In an embodiment, the heat supply is an electric heater thermallycoupled to the fluid line.

In an embodiment, the heat supply is a heat scavenger. The heatscavenger is thermally coupled to the fluid line. In an embodiment, theheat scavenger is thermally coupled to a lubricant separator. In anembodiment, the compressor system further includes a discharge lineconnected to the discharge port of the compressor, and the heatscavenger is thermally coupled to the discharge line. In an embodiment,the compressor system further includes a discharge muffler connected tothe discharge port of the compressor, and the heat scavenger isthermally coupled to the discharge muffler. In an embodiment, thecompressor system further includes a condenser and the heat scavenger isthermally coupled to the condenser. In an embodiment, the compressorsystem further includes a discharge housing and the heat scavengertransfers heat from the discharge housing to the fluid line.

In an embodiment, the compressor system further includes a second heatsupply. In an embodiment, the first heat supply is an electric heaterand the second heat supply is a heat scavenger.

In an embodiment, the compressor system further includes a controllerconnected to the heat supply. In an embodiment, the compressor systemfurther includes a flow control device that is connected to thecontroller. In an embodiment, the controller controls operation of theheat supply and the flow control device based on operational parametersof the compressor. In an embodiment, the operational parameters of thecompressor are a saturated suction temperature of the compressor, asaturated discharge temperature of the compressor, and/or compressorspeed. The operational parameters may reflect, for example, atemperature of the lubricant affecting, for example, the quantity of therefrigerant dissolved in the lubricant and/or the viscosity of thelubricant.

A method embodiment includes separating a lubricant from a discharge ofthe compressor, directing the lubricant into a fluid line, heating thelubricant using a heat source thermally coupled to the fluid line, andafter heating the lubricant, directing the lubricant to a lubricantinlet of the compressor.

In an embodiment, the heat source includes a component that sources heatseparate from the compressor, such as for example an electric heater. Inan embodiment, the heat source includes a heat scavenger thermallycoupled to the fluid line and also thermally coupled to the compressorsystem at a location separate from the fluid line.

In an embodiment, the method further includes restricting the flow oflubricant, and determining, using a processor, a lubricant volume and alubricant temperature, where restricting the flow of the lubricant iscontrolled based on the determined lubricant volume and heating thelubricant is based on the determined lubricant temperature.

In an embodiment, the lubricant volume and the lubricant temperature aredetermined by the processor based on an operating map of the compressor.

FIG. 1 shows a system diagram of a compressor system 1100 according toan embodiment. Compressor system 1100 includes a compressor 1102.Compressor 1102 has suction port 1104, discharge port 1106, andlubricant inlet 1108. A discharge line 1110 is connected to dischargeport 1106. Discharge line 1110 extends to lubricant separator 1112. Afluid line 1114 connects the lubricant separator 1112 to the lubricantinlet 1108 of compressor 1102. Lubricant separator 1112 is connected tolubricant storage 1132. Heater 1116 is thermally coupled to fluid line1114. Fluid line 1114 may include a flow control device 1118. The heater1116 and/or the flow control device 1118 may be connected to acontroller 1120.

Compressor 1102 is a compressor connected to a refrigeration circuit.Compressor 1102 compresses a fluid received at suction port 1104, andexpels the compressed fluid at discharge port 1106. The compressor 1102may be, for example, a screw compressor, where compression chambers areformed and a fluid such as a refrigerant are compressed by the rotationof two rotors and the engagement of lobes on each of the rotors.Compressor 1102 may include one or more bearings receiving lubricanttaken in at lubricant inlet 1108. The bearings may, for example, supportand allow the rotation of components of the compressor such as therotors of a screw compressor.

Compressor 1102 is part of a refrigeration circuit also includingcondenser 1122, an expansion device 1124, for example and expansionvalve, and an evaporator 1126.

Compressor 1102 includes suction port 1104. Suction port 1104 is a portlocated on compressor 1102 where the fluid to be compressed enters thecompressor. In an embodiment, one or more sensors 1128 may be located atthe suction port 1104 to measure parameters including, for example, thetemperature and the pressure of the fluid at the suction port 1104.

Compressor 1102 also includes discharge port 1106. Discharge port 1106is where compressed fluid exits the compressor 1102. The fluid exitingdischarge port 1106 includes both the fluid such as refrigerant and alsolubricant from the bearings of compressor 1102. Fluid exits dischargeport 1106 into discharge line 1110. The fluid at discharge port 1106 isat a higher temperature and pressure than the fluid entering compressor1102 at suction port 1104. One or more sensors 1130 may be located atthe discharge port 1106 to measure parameters including pressure and/ortemperature of the fluid as it exits the compressor 1102. In anembodiment, sensors 1130 may be located within the compressor 1102between suction port 1104 and discharge port 1106.

Compressor 1102 further includes lubricant inlet 1108. Lubricant inlet1108 directs lubricant into a bearing cavity 1134 of compressor 1102,which contains one or more bearings 1136. The lubricant inlet may be,for example, a port on a bearing cover or a housing of the compressor1102 extending into a bearing cavity 1134 receiving lubricant from thelubricant inlet 1108.

Discharge line 1110 is a fluid line extending from discharge port 1106of compressor 1102. Discharge line 1110 conveys fluid from the dischargeport of the compressor to the refrigeration circuit in which compressor1102 is incorporated. The fluid discharged at discharge port 1106 andconveyed by discharge line 1110 includes a fluid such as a refrigerantused in the refrigeration circuit and further includes lubricant fromthe bearings and bearing cavity of the compressor 1102.

Lubricant separator 1112 is located along discharge line 1110. Lubricantseparator 1112 separates lubricant from the flow of fluid dischargedfrom the compressor, allowing the refrigerant to continue through arefrigeration circuit, for example, a condenser, an expansion device,for example an expansion valve, and an evaporator, while removing asignificant portion of the lubricant from the flow discharged by thecompressor. Lubricant separator 1112 may include, for example, a filterconfigured to allow passage of refrigerant while trapping lubricant inthe discharge flow of the compressor. Lubricant separator may be locatedbetween discharge port 1106 of the compressor 1102 and the condenser1122 of the refrigeration circuit of compressor system 1100.

Lubricant storage 1132 stores lubricant to be provided to compressor1102. In an embodiment, lubricant storage 1132 is a sump connected tolubricant separator 1112. In an embodiment, lubricant storage 1132 is alubricant tank or the like. In an embodiment, the lubricant trapped bylubricant separator 1112 collects, for example in a pool included in thelubricant storage 1132. In an embodiment, this pool is connected tofluid line 1114 via a port. In an embodiment, lubricant storage 1132 isintegrated into lubricant separator 1112. In an embodiment, lubricantstorage 1132 is separate from lubricant separator 1112.

Fluid line 1114 is a fluid line providing fluid communication betweenlubricant storage 132 and lubricant inlet 1108 of the compressor 1102.In the embodiment shown in FIG. 1, fluid line 1114 allows lubricantrecovered at lubricant separator 1112 and stored in lubricant storage1132 to be conveyed to the bearing cavities and/or bearings ofcompressor 1102.

Heater 1116 is located along fluid line 1114. Heater 1116 is thermallycoupled to the fluid line 1114 such that heat produced by heater 1116 istransferred to fluid line 1114 and the contents of fluid line 1114. Theheater 1116 may be thermally coupled to fluid line 1114 by, for example,surrounding the fluid line 1114, having a heating element wrapped aroundor embedded in the fluid line 1114, or the like. In an embodiment,heater 1116 is an electric heater. In an embodiment, heater 1116 is anelectromagnetic induction heater.

Flow control device 1118 may be located along fluid line 1114 andconfigured to govern the flow of fluid through fluid line 1114. In anembodiment, flow control device 1118 may be, but is not limited to, acontrollable valve. Flow control device 1118 may be used to limit thequantity of lubricant flowing through fluid line 1114. In an embodiment,flow control device 1118 is upstream where heater 1116 is thermallycoupled to fluid line 1114, with respect to the direction of flow oflubricant from lubricant storage 1132 to lubricant inlet 1108. In anembodiment, flow control device 1118 allows lubricant to be heated to ahigher temperature by heater 1116 by reducing the volume of flow thatabsorbs heat provided by heater 1116. In an embodiment, the flow controldevice 1118 is a pump.

Controller 1120 may be connected to heater 1116 and/or flow controldevice 1118. Controller 1120 may receive compressor operationalinformation relevant to lubrication requirements and/or lubricantquality. The compressor operational information may include one or moreof, for example, the speed the compressor 1102 is operated at, thecapacity the compressor 1102 is operated at, a saturated suctiontemperature, saturated discharge temperature or the like. In anembodiment, the controller 1120 determines a lubricant volume and/or alubricant quality target based on the compressor operationalinformation. The determined lubricant volume may be used to control theflow control device 1118. The determined lubricant volume and/or thelubricant quality target may be used to determine an amount of heat tobe added to the lubricant by heater 1116. In an embodiment, controller1120 directs operation of heater 1116, for example, by setting theheater 1116 to supply a particular quantity of heat to fluid line 1114,operating the heater 1116 at a particular temperature or setting, oractivating and deactivating the heater 1116.

FIG. 2 shows a system diagram of a compressor system 1200 according toan embodiment. Compressor system 1200 includes compressor 1102 havingsuction port 1104, discharge port 1106, and lubricant inlet 1108,discharge line 1110, lubricant separator 1112, lubricant storage 1132,fluid line 1114, and flow control device 1118 as shown in FIG. 1 anddescribed above. The embodiment shown in FIG. 2 includes a heatscavenger 1202 that is thermally coupled to a section of the compressorsystem 1200 and to the fluid line 1114. In an embodiment, a dischargemuffler 1204 is fluidly connected to the discharge port 1106 of thecompressor 1102. In an embodiment, a condenser 1206 is locateddownstream of the compressor. Compressor 1102 and condenser 1206 arepart of a refrigeration circuit also including expansion device 1124 andevaporator 1126. In an embodiment, the compressor 1102 has a dischargehousing 1208 surrounding the discharge port 1106. In an embodiment,controller 1210 is connected to the flow control device 1118 and theheat scavenger 1202. In an embodiment, a temperature sensor 1212 isincluded in compressor system 1200. The temperature sensor 1212 may beconnected to the controller 1210 and the heat scavenger 1202.

Heat scavenger 1202 thermally couples a portion of fluid line 1114 to atleast one other part of the compressor system 1200. Heat scavenger 1202thermally couples fluid line 1114 to another part of compressor system1200. The other part of compressor system 1200 is a part that istypically at a higher temperature than the fluid line 1114, such thatthe thermal coupling transfers heat to the fluid line 1114 and heatslubricant traveling therein. The other part of the compressor system1200 may be, for example, the discharge line 1110, discharge muffler1204, condenser 1206, or discharge housing 1208. The heat scavenger 1202may include, for example, a heat-absorbing element located on, in, or atthe location on the compressor system 1200 where heat is to becollected. Heat scavenger 1202 may include one or more heat-conductingelements 1214 extending from the heat-absorbing element to the fluidline 1114. The one or more heat-conducting elements 1214 may provide thethermal coupling of the heat-absorbing element of heat scavenger 1202 tothe fluid line 1114.

In an embodiment, both a heater 1116 as described above and shown inFIG. 1 and a heat scavenger 1202 as shown in FIG. 2 are included in acompressor system. In this embodiment, both the heater 1116 and the heatscavenger 1202 are thermally coupled to the fluid line 1114. In thisembodiment, both the heater 1116 and the heat scavenger 1202 provideheat to the lubricant carried in fluid line 1114. In an embodiment, theheater 1116 is downstream of the heat scavenger 1202 with respect to aflow of lubricant through the fluid line 1114. In an embodiment, theheater 1116 and/or heat scavenger 1202 are downstream of flow controldevice 1118 with respect to a flow of lubricant through the fluid line1114.

In an embodiment, the heat-absorbing element of heat scavenger 1202 islocated on the surface of the discharge line 1110. In an embodiment, theheat-absorbing element of heat scavenger 1202 is located within thedischarge line 1110 such that the flow of fluid discharged fromcompressor 1102 into discharge line 1110 passes over the heat-absorbingelement.

In an embodiment, a discharge muffler 1204 is fluidly connected to thedischarge port 1106 of the compressor 1102. The discharge muffler 1204may be located between discharge port 1106 and discharge line 1110, oralong discharge line 1110. The discharge muffler is a muffler configuredto reduce pulsation and/or vibration resulting from the operation anddischarge of the compressor. The discharge muffler receives compressedfluid from the compressor and acts to reduce pulsation and/or vibrationresulting from the operation of compressor 1102. In an embodiment, thedischarge muffler 1204 reduces pulsation and vibration by separating thedischarge line 1110 from the rest of the refrigeration circuit by havinga gap between a part of the discharge muffler 1204 directly mechanicallyconnected to discharge line 1110 and the remainder of the refrigerationcircuit. In an embodiment, the discharge muffler 1204 reduces pulsationand/or vibration by directing the discharged fluid through a series ofbaffles, or other such feature. In an embodiment, multiple suchstructures are used to reduce pulsation and/or vibration via theircombined effects. In an embodiment, the discharge muffler 1204 isupstream of the lubricant separator 1112 with respect to the flow offluid discharged from compressor 1102. By receiving fluid at or nearwhere it is discharged from the compressor 1102, the discharge muffler1204 receives the fluid of the refrigerant circuit in a heated,compressed state. During operation of the compressor 1102, the dischargemuffler 1204, or fluid traveling through the discharge muffler 1204, istypically at a temperature that is higher than the temperature of fluidline 1114 or fluid located within fluid line 1114.

In an embodiment, the heat-absorbing element of heat scavenger 1202 islocated on the surface of the discharge muffler 1204.

In an embodiment, the heat-absorbing element of heat scavenger 1202 islocated within the discharge muffler 1204 such that the flow of fluiddischarged from compressor 1102 into discharge muffler 1204 passes overthe heat-absorbing element.

In an embodiment, a condenser 1206 is located downstream of thecompressor 1102. Condenser 1206 is a component of the refrigerationcircuit where the fluid compressed by compressor 1102 rejects heat. Inan embodiment, the condenser 1206 is downstream of lubricant separator1112 with respect to the flow of fluid discharged from compressor 1102.Condenser 1206 receives the refrigerant in a heated and compressedstate, while fluid line 1114, downstream of the lubricant separator 1112may be isolated from the heated refrigerant. Therefore, during operationof the compressor system 1200, the condenser 1206 may be at atemperature that is higher than the temperature of fluid line 1114 orfluid located within fluid line 1114. In an embodiment, theheat-absorbing element of heat scavenger 1202 is located on the surfaceof the condenser 1206. In an embodiment, the heat-absorbing element ofheat scavenger 1202 is located within the condenser 1206 such that theflow of fluid within condenser 1206 passes over the heat-absorbingelement.

In an embodiment, the compressor 1102 has a discharge housing 1208surrounding the discharge port 1106. Discharge housing 1208 is a portionof the housing of compressor 1102 that is at or near the discharge port.The heat produced when operating the compressor and heat from thecompressed fluid itself are absorbed by discharge housing 1208. Whencompressor 1102 is in operation, discharge housing 1208 is typically ata temperature higher than discharge line 1114 or fluid located insidedischarge line 1114. In an embodiment, the heat-absorbing element ofheat scavenger 1202 is located on the surface of the discharge housing1208.

Controller 1210 is connected to flow control device 1118. In anembodiment, controller 1210 is connected to temperature sensor 1212 andis configured to receive temperature data from temperature sensor 1212.Controller 1210 is configured to control flow control device 1118 todetermine an amount of lubricant to provide to the compressor 1102 basedon, for example, the operating conditions of compressor 1102, such asthe speed or capacity of the compressor, and the temperature data fromtemperature sensor 1212. In an embodiment, controller 1210 determines atemperature to achieve a lubricant quality target based on the operatingconditions of compressor 1102. In an embodiment, the lubricant qualitytarget is a temperature of the lubricant. In this embodiment, controller1210 determines a volume of lubricant that can be heated to thedetermined temperature by the heat scavenger 1202, based on thetemperature data. In an embodiment, controller 1210 directs flow controldevice 1118 to open or constrict to allow a flow of lubricant throughfluid line 1114 that provides the determined volume of lubricant. In anembodiment where heat scavenger 1202 is thermally coupled to more thanone part of compressor system 1200 aside from fluid line 1114, thecontroller may determine whether to isolate the heat scavenger 1202 fromone or more of the parts of the compressor system 1200. Isolation ofheat scavenger 1202 from other components of compressor system 1200 maybe based on the flow allowed through flow control device 1118. Isolationof heat scavenger 1202 from other components of the compressor system1200 may be based on the temperature of the parts of the compressorsystem 1200 aside from fluid line 1114, to ensure lubricant is at thedesired temperature at lubricant inlet 1108. In an embodiment wherethere is both a heat scavenger 1202 and a heater 1116, the controller1210 may determine a required quantity of lubricant flow. When therequired volume of lubricant flow exceeds the volume of lubricant thatcan be heated to the determined temperature by the heat scavenger 1202alone, as determined based on the temperature data, the controller 1210directs operation of the heater 1116 to heat the lubricant to thedetermined temperature, while directing the flow control device to openor constrict such that the volume of flow through fluid line 1114 is atleast the determined required quantity of lubricant. In an embodiment,the controller 1210 may determine the volume of flow through fluid line1114 based on a speed at which the compressor system 1200 is beingoperated.

One or more temperature sensors 1212 obtain temperature data at the oneor more parts of the compressor system that heat scavenger 1202 isthermally coupled to via the one or more heat-conducting elements 1214.Temperature sensor 1212 may be located, for example, on the heatscavenger 1202 or at any or all of the one or more parts of compressorsystem 1200, other than fluid line 1114, that it is thermally coupledto. Multiple temperature sensors according to 1212 may be included inembodiments of compressor system 1200. Examples of these other parts ofthe compressor system 1200 include the discharge line 1110, dischargemuffler 1204, condenser 1206, or discharge housing 1208. Temperaturesensor 1212 provides temperature data regarding the heat scavenger 1202itself or the sources of heat recovered and transferred by the heatscavenger 1202 to the fluid line 1114. The temperature data fromtemperature sensor 1212 may be supplied to controller 1210. Thetemperature data supplied to controller 1210 may be used, for example,to estimate the amount of heat that the heat scavenger 202 can provideto fluid in the fluid line 1114. Temperature sensor 1212 may be, forexample a thermistor, a thermocouple, a semiconductor-based temperaturesensor or any other suitable temperature measurement apparatus capableof measuring temperatures within the range of typical temperatures ofthe part of the compressor system 1200 or the heat scavenger 1202, forexample temperatures from at or about 0 to at or about 100° F. atsuction and from at or about 60 to at or about 250° F. at discharge ofthe compressor system 1200.

FIG. 3 shows a flow chart of a method 1300 according to an embodiment.Method 1300 optionally includes separating a lubricant from a dischargeof a compressor 1302. Method 1300 includes directing the lubricant froma lubricant storage into a fluid line 1304, restricting the flow of thelubricant in the fluid line using a flow control device 1306, heatingthe lubricant using a heat source thermally coupled to the fluid line1308, and directing the lubricant to a lubricant inlet of the compressorafter it has been heated 1310.

In an embodiment, lubricant is separated from a discharge of acompressor 1302. The compressor, such as compressor 1102, dischargescompressed gas at a discharge port, such as discharge port 1106. Thecompressed gas further includes lubricant, such as lubricant from thebearings and bearing cavity of the compressor. The lubricant may beseparated from the gas discharged by the compressor by, for example, alubricant separator such as lubricant separator 1112. The lubricant maybe stored following separation from the discharge of the compressor1302, for example in a lubricant storage such as lubricant storage 1132.

The lubricant is directed from lubricant storage into a fluid line 1304.The lubricant storage, such as lubricant storage 1132, where thelubricant is stored prior to being provided to compressor 1302, mayinclude an outlet directing the lubricant into the fluid line, such asfluid line 1114. The fluid line is a line providing fluid communicationbetween and a lubricant inlet of the compressor, such as lubricant inlet1108 of compressor 1102.

In an embodiment, the flow of the lubricant in the fluid line mayoptionally be restricted using a flow control device 1306. The flowcontrol device may be flow control device 1118 as described above. Theflow rate may be restricted based on, for example, an amount oflubricant required by the bearings of the compressor and/or the heatingcapacity of the heat source or heat sources that are used to heat thelubricant 1308. In an embodiment, the amount of flow may be restrictedbased on the heat available from the heat source, for example theheating capacity of an electric heater and/or the temperature of acompressor system element thermally coupled to a heat scavenger 1202.

The lubricant is heated using a heat source thermally coupled to thefluid line 1308. In an embodiment, the heat source is a heater such asheater 1116. In an embodiment, the heat source is a heat scavenger suchas heat scavenger 1202 thermally coupled to another section of thecompressor system. In an embodiment, the lubricant is heated by both aheater such as heater 1116 and a heat scavenger such as heat scavenger1202.

The heating of the lubricant 1308 may be governed by a controller, suchas controller 1120 or controller 1210. The heat added to the lubricantduring heating of the lubricant 1308 or the final temperature of thelubricant at the end of heating 1308 may be determined by the controllerbased on, for example, the speed and/or discharge temperature of thecompressor. In an embodiment, the amount of heat added to the lubricantmay be varied based on the volume of the lubricant flow following therestriction at 1306. In an embodiment, the controller controls thetemperature of the lubricant entering the lubricant inlet of thecompressor by controlling the volume of lubricant that flows throughflow control device 1118.

The lubricant is directed to a lubricant inlet of the compressor afterit has been heated 1310. The lubricant may be conveyed by the fluidline, such as fluid line 1114, to a lubricant inlet such as lubricantinlet 1108, where it enters the compressor. In an embodiment, thelubricant inlet provides the lubricant to a bearing cavity of thecompressor, where the lubricant lubricates one or more bearingssupporting one or more rotating parts of the compressor, such as therotors of a screw compressor.

Aspects:

Any of aspects 1-15 may be combined with any of aspects 16-20. It isunderstood that any of aspects 1-20 can be combined with any otheraspects recited herein.

Aspect 1. A compressor system, comprising: a compressor having a suctionport, a discharge port, and a lubricant inlet; a lubricant storage; afluid line, wherein the fluid line allows fluid communication betweenthe lubricant storage and the lubricant inlet; and a heat supply,thermally coupled to the fluid line.

Aspect 2. The compressor system according to aspect 1, wherein the heatsupply is an electric heater.

Aspect 3. The compressor system according to aspect 1, wherein the heatsupply is a heat scavenger.

Aspect 4. The compressor system according to aspect 3, wherein the heatscavenger is thermally coupled to a lubricant separator.

Aspect 5. The compressor system according to any of aspects 3-4, furthercomprising a discharge line connected to the discharge port of thecompressor, and wherein the heat scavenger is thermally coupled to thedischarge line.

Aspect 6. The compressor system according to any of aspects 3-5, furthercomprising a discharge muffler connected to the discharge port of thecompressor, and wherein the heat scavenger is thermally coupled to thedischarge muffler.

Aspect 7. The compressor system according to any of aspects 3-6, furthercomprising a condenser and wherein the heat scavenger is thermallycoupled to the condenser.

Aspect 8. The compressor system according to any of aspects 3-7, whereinthe compressor further comprises a discharge housing and the heatscavenger transfers heat from the discharge housing to the fluid line.

Aspect 9. The compressor system according to any of aspects 1-8, furthercomprising a second heat supply.

Aspect 10. The compressor system according to any of aspects 1-9 furthercomprising a lubricant separator located downstream of the dischargeport of the compressor, and wherein the lubricant storage is a lubricantsump of the lubricant separator.

Aspect 11. The compressor system according to any of aspects 1-10,wherein the fluid line includes a flow control device.

Aspect 12. The compressor system according to any of aspects 1-11,further comprising a controller connected to the heat supply.

Aspect 13. The compressor system according to aspect 12, furthercomprising a flow control device, and wherein the controller isconnected to the flow control device.

Aspect 14. The compressor system according to aspect 13, wherein thecontroller controls operation of the heat supply and the flow controldevice based on operational parameters of the compressor.

Aspect 15. The compressor system according to aspect 14, wherein theoperational parameters of the compressor comprise one or more of asaturated suction temperature, a suction pressure, a suctiontemperature, a discharge temperature, a saturated discharge temperature,a discharge pressure, and a compressor speed.

Aspect 16. A method of operating a compressor system, comprising:directing a lubricant from a lubricant storage into a fluid line;heating the lubricant using a heat source thermally coupled to the fluidline; and after heating the lubricant, directing the lubricant to alubricant inlet of a compressor.

Aspect 17. The method according to aspect 16, wherein the heat sourceincludes an electric heater.

Aspect 18. The method according to any of aspects 16-17, wherein theheat source includes a heat scavenger thermally coupled to thecompressor system at a location separate from the fluid line.

Aspect 19. The method according to any of aspects 16-18, furthercomprising: determining, using a processor, a lubricant volume and alubricant temperature; and restricting the flow of the lubricant basedon the determined lubricant volume, and wherein heating the lubricant isbased on the determined lubricant temperature.

Aspect 20. The method according to aspect 19, wherein the lubricantvolume and the lubricant temperature are determined by the processorbased on an operating map of the compressor.

Compressor systems condition lubricant to allow the operation of thecompressor under an increased variety of conditions while maintainingbearing reliability. The compressor systems include a heater located ona fluid line between a lubricant separator and a lubricant inlet. Theheater may be an electric heater, or a heat scavenger transferring heatfrom other parts of the compressor system to the fluid in the fluidline. A flow control device may control the amount of lubricant passingthrough the fluid line, reducing a lubricant pressure and/or flow rate,increasing the effectiveness of adding heat to the lubricant.

Compressor Bearing Protection Using Measured Or Estimated RheologicalProperties to Control Chiller (FIGS. 4-6)

This disclosure is directed to methods and systems for the measurementof lubricant rheological properties in compressors used in chillers,particularly determining a direct measure of lubricant rheologicalproperties based on measurements at or near the bearing cavity, andoperation of compressors based on the determined lubricant rheologicalproperties.

Proper lubrication of a bearing requires that the lubricant havesufficient rheological properties, including viscosity. The rheologicalproperties may indicate whether a lubricant is properly lubricating thebearing. The rheological properties may be presented as a viscosityratio such as kappa, the ratio of the applied viscosity to a ratedviscosity, or lambda, a ratio of lubricant film thickness to surfaceasperity height in the bearing. When determining kappa values, forexample, the rated viscosity may vary depending on operationalparameters such as a speed of a compressor including the bearing.Currently, lubricant quality (i.e. a mass fraction of lubricant vs.dissolved refrigerant) is typically estimated using a dischargesuperheat (DSH) measurement of the difference between a saturationtemperature and the temperature in the discharge line, and thisestimated lubricant quality is in turn used in place of rheologicalproperties when controlling a compressor. Target DSH measurements areused when controlling compressor operations to account for lubricantquality and device longevity and safety. The use of a direct measure oflubricant rheological properties such as a kappa value improves accuracyover approaches that instead use proxies or correlated values such asDSH and lubricant quality. Further, DSH measurements capture lubricantquality at the lubricant separator, but the lubricant is in use at thebearings, which may be at different conditions and thus the behavior ofthe lubricant may deviate from what can be predicted based on DSH.Measurement of lubricant rheological properties at or near the bearingcavity provide more accurate assessments of bearing lubrication andallow bearing lubrication to be properly assessed in systems includinglubricant preparation or enrichment devices downstream from thelubricant separator with respect to the bearings. This allows a greaterportion of the operating map for the compressor to be utilized, due tothe improved understanding of bearing lubrication.

Using rheological properties expressed as a viscosity ratio such as akappa value to assess lubrication at the bearing allows factors such ascompressor speed, which affects the sufficiency of rheologicalproperties, to be accounted for. This further improves the accuracy andprecision of compressor operation in parts of the operating maptypically associated with poor lubrication at partial loads, such aslower compressor speeds, or operations at lower ambient temperatures.Improving the extent to which the full operating map of a compressor isused allows improved efficiency to be realized in systems including thecompressor, such as chillers. Improving the accuracy and precision ofbearing lubrication assessments also provides the ability to use abroader variety of refrigerants, even ones that may have increasedsolubility in the lubricant used with the compressor and that thus mayrequire more heat to be driven out of the lubricant.

A method embodiment for operating a compressor system including alubricant separator includes measuring one or more parameters of alubricant via one or more sensors within a bearing cavity of thecompressor and using the one or more parameters to determine one or morelubricant rheological properties. In an embodiment, the one or morerheological properties include a kappa value of the lubricant.

In an embodiment, the one or more parameters include a bearing cavitytemperature and a bearing cavity pressure. In an embodiment, the one ormore parameters include a bearing cavity temperature and a suctionpressure, modified according to a transfer function. In an embodiment,the one or more parameters include a refractive index of the lubricant.In an embodiment, the one or more parameters include a viscometerreading for the lubricant.

In an embodiment, the speed of the compressor is adjusted based on theone or more lubricant rheological properties. In an embodiment, thecapacity of the compressor is adjusted based on the one or morelubricant rheological properties. In an embodiment, a heater is inthermal communication with a flow path of the lubricant from thelubricant separator to the bearing cavity.

A compressor system embodiment includes a compressor including a suctionport and a bearing cavity, one or more sensors inside the bearing cavityand configured to measure one or more parameters of a lubricant, alubricant separator, and a controller configured to receive the one ormore parameters of the lubricant and determine one or more lubricantrheological properties.

In an embodiment, in the compressor system, the one or more parametersinclude a temperature in the bearing cavity and a pressure inside thebearing cavity. In an embodiment, in the compressor system, the one ormore parameters include a refractive index of the lubricant inside thebearing cavity. In an embodiment, in the compressor system, the one ormore parameters include the temperature inside the bearing cavity, and asuction pressure measured by a sensor at the suction port, and theprocessor is configured to adjust the suction pressure according to atransfer function when determining the one or more lubricant rheologicalproperties.

In an embodiment, the controller is configured to determine an adjustedspeed of the compressor based on the one or more lubricant rheologicalproperties and direct operation of the compressor at the adjusted speed.

In an embodiment, the controller is configured to determine an adjustedcapacity for the compressor based on the one or more lubricantrheological properties, and direct operation of the compressor at theadjusted capacity.

In an embodiment, the compressor system further includes a lubricantheater in thermal communication with a flow path of the lubricant fromthe lubricant separator to the bearing cavity, and wherein thecontroller is configured to direct operation of the lubricant heaterbased on the one or more lubricant rheological properties.

The rheological properties of a lubricant are flow properties of thelubricant, including, for example, one or more of the viscosity of thelubricant, the viscosity-pressure relationship of the lubricant, and thelike. One or more of the rheological properties may be determined as afunction of one or more of a lubricant viscosity reading, a lubricantrefractive index, temperature, and pressure. The temperature andpressure may be direct measurements at a location where rheologicalproperties are to be determined, such as within a bearing cavity, or maybe measurements taken at another location and transformed, for examplevia a transfer function. The rheological properties may define whetherthe bearing has sufficient lubrication to operate at sufficient levelsof reliability or longevity.

The one or more rheological properties may be presented as a ratio, suchas a viscosity ratio. The viscosity ratio may include the measuredrheological properties and minimum thresholds or preferred values forrheological properties of lubricants at a particular bearing. In anembodiment, the viscosity ratio is a kappa value, a ratio of the appliedviscosity of the lubricant over the rated viscosity for the bearing. Therated viscosity may be based on, for example, reliability and/orlongevity data for a bearing. The rated viscosity may vary based onoperational parameters at the bearing, such as a speed of rotation atthe bearing.

In an embodiment, the rheological properties and rated viscosity withrespect to obtaining the kappa value may be determined based onelasto-hydrodynamic lubrication (EHL) or hydrodynamic lubrication.Whether EHL or hydrodynamic lubrication methods are used may bedetermined based on the type of bearing, for example using EHL forlubricant used with roller bearings.

In an embodiment, the viscosity ratio may be a lambda value, a ratio ofthe oil film thickness compared to a surface asperity height in thelubricated bearing.

FIG. 4 is a front view of bearing cover 2102 of compressor 2100according to an embodiment. In an embodiment, bearing cover 2102includes temperature probe aperture 2104 and pressure probe aperture2106.

Compressor 2100 may be, for example, a screw compressor. In anembodiment, compressor 2100 is a variable volume ratio compressor.Compressor 2100 includes a bearing cavity, which is enclosed at an endby bearing cover 2102. In an embodiment, compressor 2100 is a scrollcompressor. In an embodiment, compressor 2100 is a centrifugalcompressor.

Bearing cover 2102 is a cover located at an end of a bearing cavity ofcompressor 2100. Bearing cover 2102 encloses the bearing cavity, inwhich there are bearings allowing rotation of the rotors of thecompressor.

Temperature probe aperture 2104 is an opening extending through bearingcover 2102 and allowing at least a portion of a temperature sensor to belocated within the bearing cavity. The temperature sensor may be, forexample, a thermistor, a thermocouple, a semiconductor-based temperaturesensor or any other suitable temperature measurement apparatus capableof measuring the range of typical temperatures of the bearing cavity.The temperature sensor protruding through the temperature probe aperture2104 into the bearing cavity allows a temperature within the bearingcavity to be measured directly.

In an embodiment, compressor 2100 may include two or more temperatureprobe apertures 2104. Each bearing included in the compressor may havedifferent speeds of rotation and/or local temperatures, for example in ascrew compressor, the female rotor may have a slower speed of rotationthan the male rotor. Lubricant rheological property requirements andlubricant rheological properties may vary locally even for bearings alllocated within the bearing cavity of compressor 2100, for example due todifferences in speed of rotation at each bearing. In an embodiment, onetemperature probe aperture 2104 may be provided for each bearingincluded in the bearing cavity of compressor 2100. For example,temperature measurements may be taken at or near each of the male andfemale rotors of compressor 2100 when compressor 2100 is a crewcompressor.

Pressure probe aperture 2106 is an opening extending through bearingcover 2102 and allowing at least a portion of a pressure sensor to belocated within the bearing cavity. The portion of the pressure sensormay be a probe of the sensor, configured to receive pressure and producean output representative of the pressure at or within the bearingcavity. The pressure sensor may, for example, include a force collector,and may be a piezoresistive, capacitive, electromagnetic, or other suchsensor capable of measuring pressures within the ranges typicallyoccurring within the bearing cavity. The pressure probe aperture 2106allows the pressure sensor to directly measure the pressure within thebearing cavity.

FIG. 5 is a section view of a portion of a heating, ventilation, airconditioning and refrigeration (HVACR) system 2200 including compressor2202. Compressor 2202 includes compressor housing 2204 and rotors 2206and 2208, with rotors 2206 and 2208 disposed in a space withincompressor housing 2204. Rotor 2206 and 2208 are supported at one end bybearings 2214, 2216 that are located in bearing cavity 2210. Compressorhousing 2204, the rotors 2206, 2208 and bearing cover 2212 definebearing cavity 2210. Discharge from the compressor 2202 continuesthrough the HVACR system 2200 to lubricant separator 2218, wherelubricant is captured and recirculated to bearing cavity 2210. Lubricantheater 2220 may be located along the path carrying lubricant from thelubricant separator 2218 or a lubricant sump, tank, or reservoir to thebearing cavity 2210. HVACR system 2200 may include a controller 2222 andone or more lubricant condition sensors 2224.

HVACR system 2200 is a system including a compressor circuit for heatingand/or cooling a fluid. HVACR system 2200 may be, for example, includedin a water chiller, a heat recovery system, an ice manufacturing system,or the like. HVACR system 2200 includes a compressor circuit includingcompressor 2202, condenser 2230, expansion device (e.g. an expansionvalve) 2232, and evaporator 2234.

In an embodiment, compressor 2202 is a screw compressor that compressesa refrigerant used in HVACR system 2200. Compressor 2202 includesbearings and allows mixing of lubricant for the bearings with therefrigerant it compresses. Compressor 2202 includes a suction port 2238where the refrigerant enters the compressor 2202 and a discharge port2240 where compressed refrigerant exits the compressor 2202.

Compressor housing 2204 has a suction port 2238 where gas enters and adischarge port 2240 where gas leaves the compressor housing. Compressorhousing 2204 defines a space including cavities accommodating rotors2206 and 2208. Compressor housing 2204 is configured to, in combinationwith grooves and lobes of the rotors 2206 and 2208, define compressionchambers as the rotors 2206 and 2208 are rotated.

Rotors 2206, 2208 are located within the space defined by compressorhousing 2204. Rotors 2206, 2208, may be disposed in respective cavitieswithin compressor housing 2204. The rotors are rotated when operatingcompressor 2202, and lobes of the rotors 2206 and 2208, combined withthe compressor housing, direct refrigerant from the suction port 2238 ofthe compressor 2202 and compress the refrigerant as it is moved towardsthe discharge port 2240 of compressor 2202. In an embodiment, rotors2206 and 2208 have corresponding mated lobes configured to formcompression chambers when the rotors 2206, 2208 are rotated. In anembodiment, rotor 2206 is a male rotor and rotor 2208 is a female rotor.In an embodiment, one of the rotors, such as rotor 2206, includes ashaft 2228 that is driven by a motor 2236 to rotate the rotors 2206 and2208 when the compressor 2202 is in operation. Rotors 2206 and 2208 eachhave a first end opposite the end where shaft 2228 extends from rotor2206. The first ends of each of rotors 2206 and 2208 are supported bybearings 2214, 2216.

Bearing cavity 2210 is a space defined by rotors 2206 and 2208,compressor housing 2204 and bearing cover 2212. The bearing cavity 2210contains bearings 2214 and 2216. A lubricant may be located within thebearing cavity 2210, particularly at bearings 2214, 2216, to lubricatethe bearings. The bearing cavity may receive the lubricant from, forexample, a lubricant separator 2218. A fluid pathway from lubricantseparator 2218 to bearing cavity 2210 may include or be in contact with,for example, a heater.

Bearing cover 2212 encloses an end of compressor housing 2204. Bearingcover 2212, along with compressor housing 2204 and rotors 2206 and 2208defines bearing cavity 2210. Bearing cover 2212 may include one or moreapertures, such as temperature probe aperture 2104 and pressure probeaperture 2106 described above and shown in FIG. 4, through which sensorsmay be introduced into bearing cavity 2210. In an embodiment, bearingcover 2212 includes a refractive index probe aperture. In an embodiment,bearing cover 2212 includes an aperture through which lubricant inbearing cavity can be introduced into a refractive index sensor.

Bearing 2214 supports an end 2242 of rotor 2206, and bearing 2216supports an end 2244 of rotor 2208. Bearings 2214 and 2216 may belocated at the ends of rotors 2206 and 2208 towards the discharge end ofcompressor 2202. Bearings 2214 and 2216 allow the respective rotors2206, 2208 to rotate when the compressor 2202 is operated. Bearings 2214and 2216 are lubricated by a lubricant present within bearing cavity2210. Bearings 2214 and 2216 may be, for example, mechanical bearingssuch as ball bearings, roller bearings, or the like. Compressor 2202 mayfurther include bearings 2246 and 2248 at the suction end of rotors 2206and 2208, respectively. Bearings 2246 and 2248 may receive lubricantfrom a common source with bearings 2214 and 2216.

Lubricant separator 2218 is located downstream of the discharge port2240 of compressor 2202. Lubricant separator 2218 removes lubricant fromthe flow of refrigerant discharged by compressor 2202 and returns thelubricant to bearing cavity 2210. Lubricant separator 2218 may include alubricant sump. In an embodiment, lubricant separator 2218 includes alubricant sump and lubricant heater 2220 thermally coupled to thelubricant sump.

Lubricant heater 2220 is located at the lubricant sump of lubricantseparator 2218 or along the lubricant flow path between lubricantseparator 2218 and the bearing cavity 2210. Lubricant heater 2220 maybe, for example, an electric heater. Lubricant heater 2220 may be asystem or waste heat collector thermally coupled to another part of theHVACR system 2200. Lubricant heater 2220 may be controlled based on thelubricant rheological properties within the bearing cavity 2210, forexample via controller 2222. In an embodiment, lubricant heater 2220 islocated at or within lubricant separator 2218.

In an embodiment, other lubricant conditioning devices may be betweenlubricant separator 2218 and bearing cavity 2212 in place of or inaddition to lubricant heater 2220. The lubricant conditioning devicesmay include, for example, a filter, an expansion valve or an orificeconfigured to reduce a pressure of the lubricant, or the like.

In an embodiment, the HVACR system 2200 may include controller 2222.Controller 2222 is configured to receive data from one or more sensors2224. Controller 2222 is configured to determine, based on at least oneoutput of the one or more sensors 2224, one or more lubricantrheological properties. In an embodiment, controller 2222 is furtherconfigured to control operation of the compressor 2202 based on the oneor more lubricant rheological properties.

The one or more sensors 2224 may be at least partially disposed withinbearing cavity 2210. The one or more sensors 2224 may include arefractive index sensor, a viscometer, a temperature sensor, and/or apressure sensor. Each of the one or more sensors may have at least aportion, such as a probe, protruding into bearing cavity 2210 through anaperture in bearing cover 2212. In an embodiment, the sensor is locatedentirely within bearing cavity 2210, and a connection to the controller2222 extends through an aperture in the bearing cover 2212.

In an embodiment, the one or more lubricant rheological propertiesdetermined by controller 2222 include a viscosity ratio, for example akappa value. The kappa value is the viscosity ratio of the appliedviscosity of the lubricant over the rated viscosity for that lubricant.The kappa ratio may be reflective of the surface separation at a rollingcontact such as the bearings 2214, 2216, 2246, and/or 2248. In anembodiment, the applied viscosity used to determine kappa is determinedbased on the bearing cavity temperature and pressure measured by sensors2224. The bearing cavity temperature and pressure may be used, forexample, to determine a lubricant/refrigerant mass fraction of thelubricant being provided to the bearing, which may then be used todetermine the applied viscosity. The bearing cavity temperature andpressure may be used to determine the applied viscosity directly basedon the known properties of the lubricant and the refrigerant. In anembodiment, the applied viscosity used to determine kappa is determinedbased a refractive index of the lubricant measured by sensors 2224. Therefractive index may be used, for example, to determine thelubricant/refrigerant mass fraction, which may then be used to determinethe applied viscosity. The pressure, viscosity, and temperatureproperties of the lubricant and also of the refrigerant may be used whendetermining the applied viscosity then used to determine Kappa. In anembodiment, the viscosity ratio is a function of parameters including,for example compressor speed, bearing cavity pressure, bearing cavitypressure, refrigerant properties, lubricant properties, lubricantquality (i.e. lubricant and refrigerant mass fractions) and bearingsize. In an embodiment, the applied viscosity used to determine Kappa isdetermined directly using a viscometer, and the following function todetermine Kappa:

${Kappa} = \frac{{Viscometer}\mspace{14mu}{cSt}}{4500*( {( {RPM^{- {0.5}}} )*( {{Bearing}\mspace{14mu}{Mean}\mspace{14mu}{Diameter}^{- {0.5}}} )} }$

In an embodiment, a sensor 2226 may be located at the suction 2238 ofcompressor 2202. Sensor 2226 may be, for example a temperature sensor ora pressure sensor. Sensor 2226 may be connected to controller 2222. Inan embodiment where sensor 2226 is a temperature sensor, the saturatedsuction temperature of compressor 2202 may be adjusted by controller2222 according to a transfer function and the adjusted value used indetermining the lubricant rheological properties. In an embodiment wheresensor 2226 is a pressure sensor, suction pressure measured by sensor2226 may be used by controller 2222 to determine a value for bearingcavity pressure to use when determining lubricant rheologicalproperties.

FIG. 6 is a flow chart of a method 2300 of operating a chiller accordingto an embodiment. Lubrication rheological property parameters areobtained 2302. The lubrication rheological property parameters are usedto determine one or more lubricant rheological properties 2304. In anembodiment, the one or more lubricant rheological properties are used todetermine an updated compressor operational profile 2306. The compressoris then operated in accordance with the updated compressor operationalprofile 2308. In an embodiment, a device affecting lubricant rheologicalproperties is operated based on the determined one or more lubricantrheological properties 2310.

One or more lubrication rheological property parameters are obtained2302 at or near the bearing cavity, such as bearing cavity 2210described above and shown in FIG. 5. In an embodiment, the one or morelubrication rheological property parameters are a pressure, measured bya pressure sensor located in the bearing cavity, and a temperature,measured by a temperature sensor located in the bearing cavity. In anembodiment, the one or more lubrication rheological property parametersinclude a refractive index of the lubricant. In this embodiment, therefractive index may be obtained by a sensor located within a bearingcavity, evaluating a sample of the lubricant within the bearing cavity.In an embodiment, the one or more lubrication rheological propertyparameters include a viscometer reading of the lubricant. The one ormore lubrication rheological property parameters may be measured atlocations outside the bearing cavity but proximate to the bearing cavitywith respect to a flow of refrigerant through a compressor circuit. Thelocations outside the bearing cavity may include, for example, thesuction port of the compressor, one or more points within the compressorbut separate from the bearings, or between the discharge of thecompressor and the lubricant separator. In an embodiment, the one ormore lubrication rheological property parameters are a suction pressuremeasured at the suction port of the compressor and a bearing cavitytemperature. In an embodiment, the lubrication rheological propertyparameters are a suction pressure of the compressor measured at thesuction port of the compressor and a bearing cavity temperature. In anembodiment, a function using a saturated suction temperature, saturateddischarge temperature, discharge temperature, and compressor speed maybe used to determine a value corresponding to the bearing cavitytemperature, which can be used to determine the lubricant rheologicalproperties when combined with suction pressure.

The one or more lubrication rheological property parameters are used todetermine one or more lubrication rheological properties 2304. Aprocessor may be used to determine the lubrication rheologicalproperties. In an embodiment, the lubrication rheological propertiesinclude viscosity ratio, for example a kappa value. The kappa value isthe viscosity ratio of the lubricant, a ratio of the actual viscosity tothe rated viscosity for the lubricant. The larger the kappa value is,the better the lubricant is performing. The kappa value of lubricant mayneed to exceed certain thresholds based on the operational state of thecompressor, such as the speed at which the compressor is operating. Thekappa value may be determined by a function using the one or morelubrication rheological property parameters. In an embodiment, the oneor more rheological properties may be a lambda value, a ratio of oilfilm thickness to a surface asperity height of the bearing. In anembodiment, the lubrication rheological properties may be used todetermine a compressor component life expectancy.

The one or more lubrication rheological properties may be used todetermine an updated compressor operational profile 2306. The updatedcompressor operational profile may include one or more of a position ofa valve, a minimum speed for the compressor, or the like. The updatedcompressor operational profile 2306 may be determined, for example,based on a lookup table of permissible compressor operation, such ascapacity and/or speed at given values of lubricant rheologicalproperties. In an embodiment, the updated compressor operational profiledetermined at 2306 may be a change to the minimum speed of thecompressor. In an embodiment, the change to the minimum speed of thecompressor may be periodic changes to minimum speed. In an embodiment,the minimum speed may be increased at or near a minimum threshold valuefor the lubrication rheological properties. In an embodiment, the one ormore rheological properties may include a viscosity ratio that is afunction of parameters including compressor speed, and that viscosityratio function may be used to determine a speed included in the updatedcompressor operational profile. In an embodiment, the relationshipbetween the lubrication rheological properties and speed used todetermine the minimum speed may be the following formula:

${Kappa} = \frac{{Applied}\mspace{14mu}{Viscosity}}{4500*( {( {RPM^{- {0.5}}} )*( {{Bearing}\mspace{14mu}{Mean}\mspace{14mu}{Diameter}^{- {0.5}}} )} }$

The compressor may then be operated according to the updated compressoroperational profile 2308. Operating the compressor according to theupdated compressor operational profile may include, for example,operating the compressor at a particular speed or capacity. In anembodiment, operating the compressor at a particular speed may beperformed by controlling a variable speed drive (VSD) of the compressor.In an embodiment, operating the compressor at the particular capacitymay be performed by controlling the position of an expansion device,such as an electronic expansion valve (EXV). In an embodiment, the oilreturn from an evaporator may be controlled based on the lubricantrheological properties. In an embodiment, the oil return from anevaporator may be reduced in amount when lubricant rheologicalproperties indicate insufficient lubrication. In an embodiment, thetiming of oil return from an evaporator may be accelerated when one ormore lubricant rheological properties are above a threshold, and slowedwhen one or more lubricant rheological properties are at or near thethreshold.

In an embodiment, operating the compressor according to the updatedcompressor operational profile may include regular sampling orcontinuous monitoring of the lubricant rheological properties, and whenone or more lubricant rheological properties satisfy a threshold, apredetermined pressure differential may be used for the current loadpoint of the compressor. The predetermined pressure differential may bea standard operating pressure for the compressor, based on an efficiencycurve for that compressor.

In an embodiment, a device affecting lubricant rheological propertiesmay be operated based on the determined lubricant rheological properties2310. In an embodiment, the device affecting lubricant rheologicalproperties is a heater, thermally coupled to at least part of the flowpath of the lubricant from an oil separator to the bearing cavity. In anembodiment, the heater is an electric heater. In an embodiment, theheater is a system or waste heat collector thermally coupled to anotherpart of the HVACR system. The operation of the device affectinglubricant rheological properties may be controlled based on, forexample, whether one or more lubricant rheological properties satisfy athreshold value. In an embodiment, the device affecting lubricantquality is a controllable expansion valve or orifice, configured toreduce the pressure of the lubricant by a controlled amount. In anembodiment, the device affecting lubricant quality is a drive (e.g.variable speed drive) and/or a motor that may provide heat to gas in thecompressor system.

Determining lubricant rheological properties at or near the bearingcavity, instead of using more remote or indirect measurements oflubrication, can allow more efficient use of lubricant enrichmentdevices such as heaters and can improve the amount of the operationalmap that can be used during compressor operations. This can allowimproved efficiency for compressor operations, for example in variablevolume ratio compressors, and under conditions where lubricantrheological properties may be insufficient, such as low ambienttemperatures or at low compressor speeds.

Aspects:

Any of aspects 1-9 can be combined with any of aspects 10-18. It isunderstood that any of aspects 1-18 can be combined with any otheraspects recited herein.

Aspect 1. A method for operating a compressor system including alubricant separator, comprising: measuring one or more parameters of alubricant via one or more sensors within a bearing cavity of thecompressor; and determining one or more lubricant rheological propertiesbased on the one or more parameters.

Aspect 2. The method according to aspect 1, wherein the one or moreparameters include a bearing cavity temperature.

Aspect 3. The method according to aspect 2, wherein the one or moreparameters further includes a bearing cavity pressure.

Aspect 4. The method according to aspect 2, further comprising measuringa suction pressure of the compressor, and wherein determining the one ormore lubricant rheological properties is based on the one or moreparameters and the suction pressure, and determining the one or morelubricant rheological properties comprises applying a predeterminedtransfer function to the suction pressure of the compressor.

Aspect 5. The method according to any of aspects 1-4, wherein the one ormore parameters include a refractive index of the lubricant.

Aspect 6. The method according to any of aspects 1-5, wherein the one ormore lubricant rheological properties include a kappa value of thelubricant.

Aspect 7. The method according to any of aspects 1-6, further comprisingdetermining, via the controller, an adjusted speed of the compressorbased on the one or more lubricant rheological properties; and operatingthe compressor at the adjusted speed.

Aspect 8. The method according to any of aspects 1-7, further comprisingdetermining, using the controller, an adjusted capacity for thecompressor based on the one or more lubricant rheological properties,and operating the compressor at the adjusted capacity.

Aspect 9. The method according to any of aspects 1-8, further comprisingoperating a heater based on the one or more lubricant rheologicalproperties, wherein the heater is in thermal communication with a flowpath of the lubricant from the lubricant separator to the bearingcavity.

Aspect 10. A compressor system, comprising: a compressor, including asuction port and a bearing cavity; one or more sensors located insidethe bearing cavity and configured to measure one or more parameters of alubricant; and a processor, configured to receive the one or moreparameters of the lubricant from the one or more sensors and todetermine one or more lubricant rheological properties.

Aspect 11. The compressor system according to aspect 10, wherein the oneor more parameters include a temperature of the bearing cavity and apressure within the bearing cavity.

Aspect 12. The compressor system according to any of aspects 10-11,wherein the one or more parameters include a refractive index of thelubricant inside the bearing cavity

Aspect 13. The compressor system according to any of aspects 10-12,wherein the one or more lubricant rheological properties include a kappavalue of the lubricant.

Aspect 14. The compressor system according to any of aspects 10-13,further comprising a sensor measuring a suction pressure of thecompressor, and wherein the processor is configured to determine the oneor more lubricant rheological properties based on a bearing cavitytemperature and the suction pressure.

Aspect 15. The compressor system according to any of aspects 10-14,wherein the controller is configured to determine an adjusted speed ofthe compressor based on the one or more lubricant rheological propertiesand direct operation of the compressor at the adjusted speed.

Aspect 16. The compressor system according to any of aspects 10-15,wherein the controller is configured to determine an adjusted capacityfor the compressor based on the one or more lubricant rheologicalproperties, and direct operation of the compressor at the adjustedcapacity.

Aspect 17. The compressor system according to any of aspects 10-16,further comprising a lubricant heater in thermal communication with aflow path of the lubricant from the lubricant separator to the bearingcavity, and wherein the controller is configured to direct operation ofthe lubricant heater based on the one or more lubricant rheologicalproperties.

Aspect 18. The compressor system according to any of aspects 10-17,wherein the one or more sensors include a viscometer and the one or moreparameters include a viscosity of the lubricant.

This disclosure is directed to determining one or more lubricantrheological properties in a compressor system based on measurementstaken at or near a bearing cavity of the compressor. The measurementsmay include a viscometer reading, a refractive index, a bearing cavitypressure and a bearing cavity temperature, or a bearing cavitytemperature and a suction pressure of the compressor. The one or morelubricant rheological properties may be used to adjust compressoroperations including compressor capacity and/or compressor speed. Theone or more lubricant rheological properties may be used to control oneor more lubricant rheological property management devices such as aheater and/or an expansion valve.

Methods and Systems for Fan Control Based on Lubricant Characteristics(FIGS. 7-10)

At many operating conditions, a chiller may not be operating at fullload. For chillers that have variable speed fan(s) and/or fans with amultiple number of fan stages or discrete steps, and that have variablespeed or variable load compressor(s) and/or multiple fixed speedcompressors that can be staged on/off, a fan speed based on chilleroperating condition can be obtained via fan control in the HVAC systemsto achieve target power consumption (e.g., power optimization) in thechiller at various unloaded conditions, i.e. conditions not at full loador conditions at partial load.

The HVACR system includes a heat transfer circuit to heat or cool aprocess fluid (e.g., air, water and/or glycol, or the like). A workingfluid flows through the heat transfer circuit and is utilized to heat orcool the process fluid. In an embodiment, the working fluid includes oneor more refrigerants. There has been recent movement (e.g., the KigaliAmendment to the Montreal Protocol, the Paris Agreement, United States'Significant New Alternatives Policy (“SNAP”)) to limit the types ofrefrigerants utilized in HVACR systems as concern about environmentalimpact (e.g., ozone depletion, global warming impact) has increased. Inparticular, the movement has been to replace ozone depletingrefrigerants (e.g., chlorofluorocarbons (CFCs), hydrochlorofluorocarbons(HCFCs), or the like) and high global warming potential refrigerantswith refrigerants that have a lower environmental impact.

The replacement refrigerants are non-ozone depleting, flammable ornon-flammable, energy efficient, compatible with the materials of theheat transfer circuit and its equipment, low in toxicity, and chemicallystable over the life of the equipment of the heat transfer circuit. Forexample, previous refrigerants having relatively higher GWPs such asR134a or the like, are being replaced with refrigerants such as, but notlimited to, R1234ze (e.g., R1234ze(E)), R513A, and the like.

The heat transfer circuit includes a compressor that compresses theworking fluid. Lubricant is supplied to the compressor to providelubrication for its moving parts. A lubricant may include one or moretypes of lubricants. For example, a lubricant be, but is not limited to,polyolester (POE) oils, or the like. The lubricant is discharged fromthe compressor with the working fluid. Thus, the working fluiddischarged from the compressor contains lubricant. In some heat transfercircuits, the lubricant is also separated from the working fluid and theseparated lubricant is circulated back to the compressor. In other heattransfer circuits, the lubricant is circulated with the working fluidand is then supplied through a suction inlet of the compressor as partof the working fluid. The working fluid may also include one or moreadditional components other than lubricant(s) and refrigerant(s). Forexample, an additional component may be, but is not limited to,impurities, refrigeration system additives, tracers, ultraviolet (“UV”)dyes, and/or solubilizing agents.

Various issues may arise with the use of the newer/replacementrefrigerants due to having different properties relative to previousrefrigerants such as R134a. For example, newer refrigerants with lowerGWPs such as R1234ze (e.g., R1234ze(E)), R513A, and the like are moresoluble in the lubricant relative to previous refrigerants such as R134adue to their chemical structures. Accordingly, the lubricant providedback to the compressor contains a higher concentration of refrigerant.The higher concentration of refrigerant decreases the viscosity of thelubricant, which reduces the amount of lubrication (“lubricity”)provided by the lubricant. In particular, when a compressor is operatedat certain operating conditions, the lubricant provided to the bearingsof the compressor may not provide adequate lubricity due to theconcentration of refrigerant in the lubricant being too high. Thecompressor might be operated to avoid operation conditions wherelubricity of the lubricant becomes an issue. However, this may result inbeing unable to use certain areas of the operating map of a compressorthat may be efficient for a desired operation of the compressor (e.g.,desired flow rate of working fluid discharged by a compressor, a desiredpressure for the discharged working fluid, or the like).

Lubricant (e.g., oil and/or oil/refrigerant mixture) characteristicsinclude, for example, lubricant quality (e.g. the mass fraction of therefrigerant dissolved in the lubricant), lubricant viscosity, andlubricant kappa value. Lubricant characteristics concern can be greaterwith more efficient compressor(s). As the compressor becomes moreefficient, at a low ambient temperature with low compressor load, thedischarge superheat can be relatively low. Low discharge superheat canresult in less than sufficient lubricant characteristics such aslubricant quality. Lubricant characteristics such as lubricant qualitycan be a function of discharge superheat. The embodiments describedherein can determine a less efficient chiller operation which makes thecompressor work a little harder (less efficient) for the same load,increases the discharge superheat, and achieves target lubricantcharacteristics.

In an embodiment, a method of controlling condenser fans in an HVACsystem is provided. The method includes obtaining, by a controller, ameasurement of a measureable parameter of the HVAC system. The methodalso includes determining, by the controller, a differential pressurebetween a condenser and an evaporator based on the measurement and apredetermined threshold (e.g., a threshold for the discharge superheat).The method further includes outputting, by the controller, a fan speedsuitable to achieve the differential pressure determined. Also themethod includes controlling one or more condenser fans based on anoutput of the fan speed to obtain a fan capacity suitable to control theone or more condenser fans, such that power of the HVAC system ismanaged through a power consumed by a compressor and the one or morecondenser fans. The measureable parameter is indicative of lubricantcharacteristics.

In an embodiment, an HVAC system is provided. The system includes acompressor, an evaporator fluidly connected to the compressor, acondenser fluidly connected to the compressor, and a controller. Thecondenser includes one or more condenser fans. The controller isoperatively connected to a device to measure a measureable parameter ofthe HVAC system, is configured to obtain a measurement of themeasureable parameter, and is operatively connected to the condenserincluding the one or more condenser fans. The controller is alsoconfigured to determine a differential pressure between the condenserand the evaporator based on the measurement and a predeterminedthreshold. The controller is further configured to determine a fan speedsuitable to achieve the differential pressure determined. Also thecontroller is configured to operate the one or more condenser fans basedon an output of the fan speed to obtain a fan capacity suitable tocontrol the one or more condenser fans, such that the power of the HVACsystem is managed through power consumed by the compressor and the oneor more condenser fans. The measureable parameter is indicative oflubricant characteristics.

Other features and aspects will become apparent by consideration of thefollowing detailed description and accompanying drawings.

This disclosure relates generally to fan control for HVAC systems. Morespecifically, the disclosure relates to methods and systems forcontrolling fan(s) to achieve a balance between compressor(s) and fan(s)for target lubricant characteristics for HVAC system(s). “Target”lubricant characteristics refer to, for example, a lubricity of thelubricant provided to the compressor where the compressor can operate atthe full operating map with such lubricant having the lubricity. It willbe appreciated that “target” lubricant characteristics can refer to oneor more of the lubricant characteristics that exceeds the minimumrequirement for operation. It will also be appreciated that “target”lubricant characteristics can refer to an optimal lubricantcharacteristic. It will also be appreciated that “target” efficiency ofthe chiller can refer to an optimal efficiency of the chiller. The“target” efficiency of the chiller can be achieved by, for example,determining a fan speed to minimize total power consumption at thechiller capacity by using the compressor load and the ambienttemperature.

For chillers that have variable speed fan(s) and/or fans with a multiplenumber of fan stages or discrete steps, and that have variable speed orvariable load compressor(s) and/or multiple fixed speed compressors thatcan be staged on/off, a fan speed based on chiller operating conditioncan be obtained via fan control in the HVAC systems to achieve targetpower consumption (e.g., power optimization) in the chiller at variousunloaded conditions, i.e. conditions not at full load or conditions atpartial load. U.S. Pat. No. 9,810,469, which is incorporated herein byreference in its entirety, describes a fan speed control system todetermine a fan speed to minimize total power consumption at the chillercapacity, based on various operating conditions of compressor load andambient air temperature.

In one embodiment, lubricant characteristics can be a function ofdischarge superheat. Lubricant characteristics concern(s) can be greaterwith more efficient compressor(s). As the compressor becomes moreefficient, at a low ambient temperature with low or partial compressorload, the discharge superheat can be relatively low. Higher compressorefficiency can result in lower discharge superheat. Low dischargesuperheat can result in less than sufficient lubricant characteristics.The embodiments described herein can determine a less efficient chilleroperation which makes the compressor work a little harder (lessefficient) for the same load, increases the discharge superheat, andachieves target lubricant characteristics. High lubricantcharacteristics (such as target or better than target lubricantcharacteristics) can ensure a long lifecycle of the compressor. It willbe appreciated that the chemistry of which type of refrigerant is used,and/or which type of lubricant is used can determine the sensitivity ofthe lubricant characteristics when the discharge superheat changes.

FIG. 7 shows a schematic view of a chiller in an HVAC system to controlfan(s). FIG. 7 shows one embodiment of a chiller (such as an air cooledchiller) that has a compressor 3001, an evaporator 3003, a condenser3004 with air coil 3005 and fans 3008, and a control unit 3002 and panel3007. It will be appreciated that the compressor 3001 can be a variablespeed compressor or a variable load compressor and/or one of themultiple fixed speed compressors that can be staged on/off, and that thefans 3008 can be variable speed fan(s) and/or fan(s) with a multiplenumber of fan stages or discrete steps. The condenser 3004 and its aircoil 3005 in the embodiment shown are one example of an air cooledcondenser, however it will be appreciated that the specific condenser3004/coil 3005 combination shown is merely exemplary. The chiller can beconsidered a single unit within the HVAC system and be supported by aframe 3006 for example. It will be appreciated that the specificconfiguration shown in FIG. 7 is merely exemplary, as other chillerdesigns, layouts, and specific configurations may be employed. Forexample, the chiller of FIG. 7 can be a chiller with “W” shaped coils;however, it will be appreciated that other coil types may be used, suchas for example multiple “V” shaped coils or more than one circuitemploying multiple compressors, evaporators, condensers. Generally, themethods and systems to control fan can be employed in any type ofchiller with variable speed fan(s) and/or with fan(s) that have amultiple number of fan stages or discrete steps and variable speed (orvariable load) compressor(s) and/or multiple fixed speed compressorsthat can be staged on/off.

FIG. 8 illustrates fan control 3200 that can include devices to detect,obtain, or otherwise determine the inputs needed for a controller todetermine the appropriate output to control fan(s). In one embodiment, adevice 3205 is used to measure a measureable parameter (e.g.,temperature, pressure) of an HVAC system. The device 3205 communicatesthe measurement to a controller 3210. The controller 3210 uses themeasurement to obtain a superheat (e.g., the discharge superheat). Thecontroller 3210 can control the fan(s) 3215 based on the obtainedsuperheat and target lubricant characteristics (e.g., the predeterminedlubricity of the lubricant where the compressor can operate at the fulloperating map with such lubricant, or predetermined discharge superheatbecause lubricant characteristics can be a function of dischargesuperheat). The device 3205 can periodically update the measurementstaken as needed and/or desired, such as automatically, during/after anoperation change or changing conditions of the chiller, and/or manually.It will be appreciated that the controller 3210 can use the most recentmeasurement data available unless otherwise specified.

The controller 3210 can be implemented into, for example, control unit3002 and panel 3007 in FIG. 7. It will be appreciated that the controlunit 3002, such as shown in the chiller of FIG. 7, generally can includea processor (not shown), a memory (not shown), and optionally a clock(not shown) and an input/output (I/O) interface (not shown), and thecontrol unit 3002 can be configured to receive data as input fromvarious components within an HVAC system, such as the components shownin FIG. 7 and FIG. 8, and can also send command signals as output tovarious components within the HVAC system.

In one embodiment, superheat can be defined as a difference between theactual temperature of the refrigerant vapor and the saturationtemperature (boiling point) of the refrigerant at the same measuringlocation. In one embodiment, the saturation temperature (boiling point)of the refrigerant can be obtained by measuring a pressure (e.g.,discharge pressure or suction pressure) of the refrigerant by using, forexample, a pressure sensor, a gauge, and then converting the measuredpressure to a temperature (saturation temperature). In an embodiment,the device 3205 can include a pressure sensor, a gauge, or the like tomeasure the pressure. The device 3205 can also include a temperaturesensor to measure the actual temperature of the refrigerant vapor. Inone embodiment, discharge superheat is the superheat obtained at thecompressor discharge side (e.g., in the lubricant separator, or in thebearing cavity), which is the measured actual temperature of therefrigerant vapor minus the obtained saturation temperature (boilingpoint) of the refrigerant at the same measuring location at thecompressor discharge side.

In one embodiment, lubricant characteristics can be a function ofdischarge superheat. Perceived low lubricant characteristics (such asless than sufficient lubricant quality) correspond to a low dischargesuperheat value. When the controller 3210 determines that the obtaineddischarge superheat drops below a predetermined value (which correspondsto the perceived low lubricant characteristics), the controller 3210 candetermine a first differential pressure (ΔPdiff) between a condenser andan evaporator (or between a compressor suction side and a compressordischarge side) to achieve target lubricant characteristics.

In one embodiment, the controller 3210 can determine a seconddifferential pressure (ΔPdiff) between a condenser and an evaporator (orbetween a compressor suction side and a compressor discharge side),based on a measured ambient air temperature and an obtained present loadon the compressor, to achieve a target (e.g., optimal) efficiency of thechiller by, for example, balancing the power requirements of thecompressor(s) and the fan(s).

It will be appreciated that the first differential pressure is toachieve target lubricant characteristics, and the second differentialpressure is to achieve target efficiency of the chiller. Both the firstdifferential pressure and the second differential pressure are used todetermine corresponding fan speed (and/or compressor speed) to achievethe target lubricant characteristics or the target efficiency. It willalso be appreciated that at a low or partial load (where efficiency isnot as important), the compressor might not generate enough superheat tokeep the target lubricant characteristics. In an embodiment, when thedischarge superheat drops below a predetermined value (which correspondsto the perceived low lubricant characteristics), the controller 3210 candetermine the first differential pressure to make the compressor workharder (corresponding to a slower fan speed) than when the compressorworks under the second differential pressure, so that the superheat (andlubricant characteristics) increases (giving up efficiency). When thedischarge superheat is at or above the predetermined value (indicativeof target lubricant characteristics), the controller 3210 can determinethe second differential pressure to make the compressor work moreefficiently (corresponding to a faster fan speed) than when thecompressor works under the first differential pressure, to achieve thetarget efficiency (in such case, the superheat (and lubricantcharacteristics such as lubricant quality) can decrease).

The ambient air temperature can be measured by, for example, atemperature sensor (not shown). The temperature sensor can communicatethe ambient temperature measurement to the controller 3210. The presentload on the compressor can be determined based on a compressor's runningspeed, which in some examples may be expressed as a percentage of ratedspeed for a particular compressor frame size, e.g. relative to thecompressor full speed configured limit. A device (not shown) can measureand communicate for example, the percentage of rated speed of thecompressor to the controller 3210. It will be appreciated that,depending on the method of unloading of the compressor, mechanicalunloader position sensor(s) may be considered to obtain the compressorload, e.g. compressor speed. In other embodiments, compressor load, e.g.compressor speed, could also be estimated indirectly such as for exampleby a change in evaporator water temperature obtained by the controllerthrough use of for example temperature sensor(s).

In operation, the controller 3210 can determine the second differentialpressure between a condenser and an evaporator, based on a measuredambient air temperature and an obtained present load on the compressor,to achieve target efficiency of the chiller. If the controller 3210determines that an obtained discharge superheat drops below apredetermined value, the controller 3210 can determine a firstdifferential pressure between the condenser and the evaporator toachieve target lubricant characteristics. It will be appreciated thatthe first differential pressure can be set to a value greater than thesecond differential pressure. With a larger differential pressure, thechiller is less efficient—the compressor works harder (less efficient)for the same load, the discharge superheat is thus increased, and targetlubricant characteristics can be achieved. When the differentialpressure is larger, typically the compressor speed is higher (forvariable speed compressors), and the fan speed is lower for the sameload. In another embodiment, for a larger differential pressure when avariable load compressor is used, an unloader can be used to change(e.g., increase) the load of the compressor; and the fan speed can bedecreased.

If the controller 3210 determines that an obtained discharge superheatis no less than the predetermined value, the controller 3210 candetermine and/or set the first differential pressure to be the same asthe second differential pressure. In such a case, both the targetlubricant characteristics and the target efficiency of the chiller canbe achieved.

It will be appreciated that the controller 3210 can use lubricantviscosity and/or lubricant kappa value instead of (or in addition to)discharge superheat, to determine the first differential pressure.

In one embodiment, the discharge superheat (and/or lubricant viscosityand/or lubricant kappa value) can be an integral of the dischargesuperheat (and/or lubricant viscosity and/or lubricant kappa value) overa predetermined period of time to track how far the discharge superheat(and/or lubricant viscosity and/or lubricant kappa value) is below thepredetermined value over time. If the integral exceeds a certain value,the controller 3210 can set the first differential pressure to a valuegreater than the second differential pressure, to achieve targetlubricant characteristics. If the integral decreases to or below thecertain value, the controller 3210 can set the first differentialpressure to be the same as the second differential pressure to alsoachieve efficiency of the chiller.

It will be appreciated that the target differential pressure (e.g., thefirst differential pressure or the second differential pressure) can beadded to the suction pressure from the compressor to obtain a targetdischarge pressure of the compressor. As the fans may change speed toreach a target discharge pressure of the compressor, the unit capacity,e.g. of the chiller, can also change to a new compressor speed. The newcompressor speed can then in turn change the output target differentialpressure across the compressor. The chilled water temperature controlthen drives the chiller to the appropriate chiller capacity.

In one embodiment, the fan control can determine the fan speed toachieve target lubricant characteristics by using the dischargesuperheat to obtain the output target differential pressure (the firstdifferential pressure). The fan control can also determine the fan speedto minimize total power consumption at that unit capacity by using thecompressor load and the ambient temperature to obtain the output targetdifferential pressure (the second differential pressure).

The output target differential pressure (the first or seconddifferential pressure) in turn can be used to determine the appropriatefan capacity, e.g. based on the resulting fan speed that can (1) meetthe target lubricant characteristics (when the first differentialpressure is used), or (2) minimize total power consumption at that unitcapacity, for example the relative power consumed by the compressor andby the fans (when the second differential pressure is used).

It will be appreciated that compressor speed in rpm can be commanded bythe controller, e.g. 3210, in response to, for example, the chillerwater temperature control loop of a water chiller. In the methods andsystems described herein, differential pressure can be the controlleroutput parameter, and discharge superheat (for the first differentialpressure) can be the input parameter used to obtain the outputparameter. In the methods and systems described herein, differentialpressure can be the controller output parameter, and compressor loadand/or ambient temperature (for the second differential pressure) can bethe input parameter used to obtain the output parameter.

It will be appreciated that the use of target differential pressure isjust one example of a control parameter obtained from the inputparameter, and is not meant to be limiting. It will be appreciated thatthe input parameter(s) could be used to output fan speed directly,rather than using them to first obtain the target differential pressure.

In some embodiments, the controller 3210 may employ a high pressureavoidance control to control fan capacity in multi-stages such as forexample, when the condensing temperature approaches the condenserpressure limit, fan capacity can be added in discrete fixed speed fanstages in systems using variable speed fan(s) and/or fan(s) with amultiple number of fan stages or discrete steps.

FIG. 9 is a flow chart of one embodiment of a method 3300 of fancontrol. The method 3300 of controlling condenser fans in an HVAC systemincludes obtaining a measurement of a measureable parameter 3305. Themeasureable parameter can be one or more of a discharge superheat, aviscosity of lubricant used in the HVAC system, or a kappa value of thelubricant. With a controller, a target differential pressure between acondenser and an evaporator can be determined 3310, which can be basedon, for example, the measureable parameter (such as the dischargesuperheat) and a predetermined threshold. If the measurement is lessthan the predetermined threshold, the controller can set thedifferential pressure (the first differential pressure) to a valuegreater than a second differential pressure between the condenser andthe evaporator, to achieve target lubricant characteristics. In oneembodiment, the second differential pressure can be based on a measuredambient air temperature and an obtained present load on the compressor.If the measurement is no less than the predetermined threshold, thecontroller can set the differential pressure (the first differentialpressure) to be equal to a second differential pressure between thecondenser and the evaporator.

With the controller, a condenser fan speed suitable to achieve a fancapacity can be outputted 3315 and that is suitable to achieve thetarget differential pressure determined. One or more variable speed fanscan be controlled 3320 based on the output of condenser fan speed toachieve the fan capacity. It will be appreciated that the fans may befans with a multiple number of fan stages or discrete steps, or acombination of variable speed fan(s) and fan(s) with a multiple numberof fan stages or discrete steps. In an embodiment, when fixed speedfan(s) with a multiple number of fan stages or discrete steps are used,for example, to drop the amount of airflows, some fan(s) can be turnedoff; to increase the amount of airflows, more fan(s) can be turned on.

Using a system with such a control method, the differential pressuretarget can be varied based on the measureable parameter (such as thedischarge superheat) to determine the fan speed, which can achievetarget lubricant characteristics. At part load and full load operationconditions, the control can determine the fan speed to obtainefficiencies in the circuit to allow trade-offs between condenser fanpower (which can increase to keep system differential pressurerelatively low) and compressor power (which can increase when systemdifferential pressure increases). In an embodiment, the objective is toachieve balance between compressor speed (or load) and the fan speed (orstaging) to provide target efficiency (e.g., for the overall chillerperformance or compressor performance) for a given capacity. In suchembodiment, the discharge superheat generated by the compressor mightnot be high enough to achieve target lubricant characteristics. As aresult, the control of the compressor speed (or load) and the fan speed(or staging) is moved from target efficiency to target lubricantcharacteristics to increase the discharge superheat (by e.g. making thecompressor to work harder or less efficient for the same load and/or bylowering the fan speed).

It will be appreciated that a differential pressure (e.g., the seconddifferential pressure) based on, for example, the compressor load andthe ambient temperature, can be used to achieve target efficiency of thechiller. A differential pressure (e.g., the first differential pressure)based on, for example, a desired discharge superheat (or lubricantviscosity, or lubricant kappa value) can be used to achieve targetlubricant characteristics. Moving from target efficiency to targetlubricant characteristics can increase the discharge superheat (and thusthe lubricant characteristics) but the efficiency of the chiller can belower (compared with target efficiency).

It will also be appreciated that in an operation map for fan control toachieve target efficiency, the fan control (e.g., fan speed control) canbe a function of the compressor speed/load and the ambient temperature.It will be appreciated that the fan control to achieve target chillerefficiency works better around minimum compressor speed (for example,1400 rpm) than at other compressor speed. It will further be appreciatedthat to achieve target lubricant characteristics, in the correspondingareas of the operating map, discharge superheat can be raised byutilizing fan control to target higher differential pressures. Thehigher pressure differential results in the compressor doing more workfor the same operating point (e.g., in the operating map) providing ahigher discharge superheat value and thus higher lubricantcharacteristics.

Testing and/or simulation show that in one embodiment, for a screwcompressor in an air cooled chiller, from a baseline configuration, whenthe power consumption of the chiller increases about 33.5% (e.g., thefan speed decreases 32% and the compressor speed increases about 4%),the discharge superheat gains about one degree (Fahrenheit). Testingand/or simulation also show that in one embodiment, for a screwcompressor in an air cooled chiller, from a baseline configuration, whenthe power consumption of the chiller increases about 68% (e.g., the fanspeed decreases 43% and the compressor speed increases about 8%), thedischarge superheat gains about four degrees (Fahrenheit). In anembodiment, the baseline configuration is based on the chiller operatingat target efficiency (e.g., optimal efficiency achieved by determining afan speed by minimizing total (e.g., compressor and fan) powerconsumption at a certain operating load and/or capacity of the chiller).

FIG. 10 shows a relationship between the system pressure differentialand the ambient temperature, according to one embodiment. In FIG. 10,the vertical coordinate is the system pressure differential (unit psid),and the horizontal coordinate is the ambient temperature. The solid linerepresents a fan control curve to achieve the maximum unit efficiency(but the lubricant characteristics (such as lubricant quality) are lowbecause of, e.g., low discharge superheat). The dotted lines representfan control curves to achieve lower (and/or further lower) unitefficiency (compared with the maximum unit efficiency) but the lubricantcharacteristics are improved (and/or further improved) because of, e.g.,increased discharge superheat.

It will be appreciated that as soon as the fan control is changed fromtarget lubricant characteristics control to target efficiency control,the dotted lines transition/merge into the solid line. It will beappreciated that lubricant characteristics can be a function ofdischarge superheat. For any given saturated discharge temperature, thelubricant characteristics improve as the discharge superheatimproves/increases.

With regard to the foregoing description, it is to be understood thatchanges may be made in detail, without departing from the scope of thepresent invention. It is intended that the specification and depictedembodiments are to be considered exemplary only, with a true scope andspirit of the invention being indicated by the broad meaning of theclaims.

Aspects:

Any of aspects 1-7 can be combined with any of aspects 8-14. It isunderstood that any of aspects 1-14 can be combined with any otheraspects recited herein.

Aspect 1. A method of controlling condenser fans in a heating,ventilation, and air conditioning (HVAC) system, comprising: obtaining,by a controller, a measurement of a measureable parameter of the HVACsystem; determining, by the controller, a differential pressure betweena condenser and an evaporator based on the measurement and apredetermined threshold; outputting, by the controller, a fan speedsuitable to achieve the differential pressure determined; andcontrolling one or more condenser fans based on an output of the fanspeed to obtain a fan capacity suitable to control the one or morecondenser fans, such that power of the HVAC system is managed through apower consumed by a compressor and the one or more condenser fans,wherein the measureable parameter is indicative of lubricantcharacteristics.

Aspect 2. The method of aspect 1, wherein the measureable parameter isone of a discharge superheat of the compressor, a viscosity of lubricantused in the HVAC system, or a kappa value of the lubricant.

Aspect 3. The method of aspect 1 or aspect 2, wherein the compressor isa variable speed compressor or a variable load compressor.

Aspect 4. The method of any one of aspects 1-3, wherein the one or morecondenser fans are variable speed fans or fans with fan stages.

Aspect 5. The method of any one of aspects 1-4, wherein the measurementis an integral of measured values of the measureable parameter over apredetermined period of time.

Aspect 6. The method of any one of aspects 1-5, further comprising:determining a second differential pressure between the condenser and theevaporator based on a measured ambient air temperature and an obtainedpresent load on the compressor, wherein if the measurement is less thanthe predetermined threshold, the differential pressure is set to greaterthan the second differential pressure.

Aspect 7. The method of any one of aspects 1-6, further comprising:determining a second differential pressure between the condenser and theevaporator based on a measured ambient air temperature and an obtainedpresent load on the compressor, wherein if the measurement is no lessthan the predetermined threshold, the differential pressure is set tothe second differential pressure.

Aspect 8. A heating, ventilation, and air conditioning (HVAC) system,comprising: a compressor; an evaporator fluidly connected to thecompressor; a condenser fluidly connected to the compressor; thecondenser including one or more condenser fans; a controller operativelyconnected to a device to measure a measureable parameter of the HVACsystem, configured to obtain a measurement of the measureable parameter,and operatively connected to the condenser including the one or morecondenser fans; the controller configured to determine a differentialpressure between the condenser and the evaporator based on themeasurement and a predetermined threshold, the controller configured todetermine of a fan speed suitable to achieve the differential pressuredetermined, and the controller configured to operate the one or morecondenser fans based on an output of the fan speed to obtain a fancapacity suitable to control the one or more condenser fans, such thatthe power of the HVAC system is managed through power consumed by thecompressor and the one or more condenser fans, wherein the measureableparameter is indicative of lubricant characteristics.

Aspect 9. The system of aspect 8, wherein the measureable parameter isone of a discharge superheat of the compressor, a viscosity of lubricantused in the HVAC system, or a kappa value of the lubricant.

Aspect 10. The system of aspect 8 or aspect 9, wherein the compressor isa variable speed compressor or a variable load compressor.

Aspect 11. The system of any one of aspects 8-10, wherein the one ormore condenser fans are variable speed fans or fans with fan stages.

Aspect 12. The system of any one of aspects 8-11, wherein themeasurement is an integral of measured values of the measureableparameter over a predetermined period of time.

Aspect 13. The system of any one of aspects 8-12, wherein if themeasurement is less than the predetermined threshold, the differentialpressure is set to greater than a second differential pressure betweenthe condenser and the evaporator, the second differential pressure isbased on a measured ambient air temperature and an obtained present loadon the compressor.

Aspect 14. The system of any one of aspects 8-13, wherein if themeasurement is no less than the predetermined threshold, thedifferential pressure is set to a second differential pressure betweenthe condenser and the evaporator, the second differential pressure isbased on a measured ambient air temperature and an obtained present loadon the compressor.

Methods and systems for controlling condenser fans in a heating,ventilation, and air conditioning (HVAC) system are provided. The methodincludes obtaining, by a controller, a measurement of a measureableparameter of the HVAC system. The method also includes determining, bythe controller, a differential pressure between a condenser and anevaporator based on the measurement and a predetermined threshold. Themethod further includes outputting, by the controller, a fan speedsuitable to achieve the differential pressure determined. Also themethod includes controlling one or more condenser fans based on anoutput of the fan speed to obtain a fan capacity suitable to control theone or more condenser fans, such that power of the HVAC system ismanaged through a power consumed by a compressor and the one or morecondenser fans.

Heat Transfer Circuit with Increased Compressor Suction Heat, andOperating Method Thereof (FIGS. 11-16)

AN HVACR system can include a heat transfer circuit configured to heator cool a process fluid (e.g., air, water and/or glycol, or the like). Aworking fluid is circulated through the heat transfer circuit. The heattransfer circuit includes a compressor for compressing the workingfluid. The working fluid and process fluid separately flow through aheat exchanger to cool or heat the process fluid. The heat exchanger maybe a condenser or an evaporator.

The working fluid is heated by a first heating that occurs due to heatexchange between the working fluid and the process fluid. A flow path ofthe working fluid through the heat transfer circuit includes a suctionstream. The suction stream extends from a location where a first heatingoccurs to the suction inlet of the compressor. The suction streamincludes a heat source. The heat source is configured to heat theworking fluid flowing through the suction stream. The heat sourceprovides a second heating of the working fluid after the first heating.

In an embodiment, the working fluid includes one or more refrigerants.

In an embodiment, the heat source is disposed after the evaporator andbefore the compressor. The heat source heats the working fluid withinthe suction stream as it flows from the evaporator to the compressor.

In an embodiment, the heat source is located in the evaporator. The heatsource is located between the location of the first heating and theoutlet of the evaporator. The heat source heats the working fluid afterit has been heated by the process fluid and before it exits theevaporator.

In an embodiment, high temperature compressed working fluid isdischarged by the compressor and utilized by the heat source to providethe heat for the second heating. The heat source is configured so thatat least a portion of the compressed working fluid flows through theheat source. Working fluid in the suction stream is heated as it flowsthrough the heat source and absorbs heat from the compressed workingfluid also flowing through the heat source. The heat source isconfigured to utilize the compressed working fluid to heat the workingfluid of the suction stream.

In an embodiment, a method of operating a heat transfer circuit includesheating a working fluid with a process fluid in an evaporator. Themethod also includes heating the working fluid with a heat source afterthe working fluid has been heated by the process fluid.

A heating, ventilation, air conditioning, and refrigeration system(“HVACR”) is generally configured to heat and/or cool an enclosed space(e.g., an interior space of a commercial building or a residentialbuilding, an interior space of a refrigerated transport unit, or thelike). The HVACR system includes a heat transfer circuit to heat or coola process fluid (e.g., air, water and/or glycol, or the like). A workingfluid flows through the heat transfer circuit and is utilized to heat orcool the process fluid. In an embodiment, the working fluid includes oneor more refrigerants. The working fluid may heat and/or cool a processfluid directly or indirectly. For example, indirect heating and/orcooling may include the working fluid heating and/or cooling anintermediate fluid (e.g., air, water and/or glycol, or the like), andthen the heated/cooled intermediate fluid heating and/or cooling theprocess fluid.

There has been recent movement (e.g., the Kigali Amendment to theMontreal Protocol, the Paris Agreement, United States' Significant NewAlternatives Policy (“SNAP”)) to limit the types of refrigerantsutilized in HVACR systems as concern about environmental impact (e.g.,ozone depletion, global warming impact) has increased. In particular,the movement has been to replace ozone depleting refrigerants (e.g.,chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), or thelike) and high global warming potential refrigerants with refrigerantsthat have a lower environmental impact.

The replacement refrigerants are non-ozone depleting, flammable ornon-flammable, energy efficient, compatible with the materials of theheat transfer circuit and its equipment, low in toxicity, and chemicallystable over the life of the equipment of the heat transfer circuit. Forexample, previous refrigerants having relatively higher GWPs such asR134a or the like, are being replaced with refrigerants such as, but notlimited to, R1234ze (e.g., R1234ze(E)), R513A, and the like.

The heat transfer circuit includes a compressor that compresses theworking fluid. Lubricant is supplied to the compressor to providelubrication for its moving parts. A lubricant may include one or moretypes of lubricants. For example, a lubricant may be, but is not limitedto, one or more polyolester (POE) oils, mineral oils, or the like. Thelubricant is discharged from the compressor with the working fluid.Thus, the working fluid discharged from the compressor containslubricant. In some heat transfer circuits, the lubricant is alsoseparated from the working fluid and the separated lubricant iscirculated back to the compressor. In other heat transfer circuits, thelubricant is circulated with the working fluid and is then suppliedthrough a suction inlet of the compressor as part of the working fluid.The working fluid may also include one or more additional componentsother than lubricant(s) and refrigerant(s). For example, an additionalcomponent may be, but is not limited to, impurities, refrigerationsystem additives, tracers, ultraviolet (“UV”) dyes, and/or solubilizingagents.

Various issues may arise with the use of newer/replacement refrigerantsdue to having different properties relative to previous refrigerantssuch as R134a. For example, newer refrigerants with lower GWPs such asR1234ze (e.g., R1234ze(E)), R513A, and the like may be more soluble inthe lubricant relative to previous refrigerants such as R134a due totheir chemical structures. Accordingly, the lubricant provided back tothe compressor contains a higher concentration of refrigerant. Thehigher concentration of refrigerant decreases the viscosity of thelubricant, which reduces the amount of lubrication (“lubricity”)provided by the lubricant. In particular, when a compressor is operatedat certain operating conditions, the lubricant provided to the bearingsof the compressor may not provide adequate lubricity due to theconcentration of refrigerant in the lubricant being too high. Thecompressor might be operated to avoid operation conditions wherelubricity of the lubricant becomes an issue. However, this may result inbeing unable to use significant areas of the operating map of acompressor that are most efficient for a desired operation of thecompressor (e.g., desired flow rate of working fluid discharged by acompressor, a desired pressure for the discharged working fluid, or thelike). As such, the incorporation and use of newer/replacementrefrigerants may result in compressors being operated in a lessefficient manner to avoid lubrication issues. Embodiments describedherein are directed to heat transfer circuits and methods of operating aheat transfer circuit that help reduce and/or avoid such lubricationissues without having to avoid specific operating conditions of acompressor due to, for example, the use of newer/replacementrefrigerants.

FIG. 11 is a schematic diagram of a heat transfer circuit 4001 accordingto an embodiment. In an embodiment, the heat transfer circuit 4001 maybe employed in an HVACR system. The heat transfer circuit 4001 includesa compressor 4010, a condenser 4020, an expansion device 4030, anevaporator 4040, and a heat source 4050. Optionally, the heat transfercircuit 4001 may also include a lubricant separator 4060 as shown inFIG. 11. In an embodiment, the heat transfer circuit 4001 can bemodified to include additional components such as, for example, aneconomizer heat exchanger, one or more flow control devices, a receivertank, a dryer, a suction-liquid heat exchanger, or the like.

The components of the heat transfer circuit 4001 are fluidly connected.The heat transfer circuit 4001 can be configured as a cooling system(e.g., a fluid chiller of an HVACR system, an air conditioning system,or the like) that can be operated in a cooling mode, or the heattransfer circuit 4001 may be configured to operate as a heat pump systemthat can run in a cooling mode or a heating mode.

A working fluid flows through the heat transfer circuit 4001. The flowpath of the working fluid through the heat transfer circuit 4001 extendsfrom the compressor 4010 through the lubricant separator 4060, thecondenser 4020, the expansion device 4030, the evaporator 4040, the heatsource 4050, and back to the compressor 4010. The working fluid includesone or more refrigerants with a lower environmental impact and mayinclude one or more additional components as discussed above. Dottedlines are provided in the Figures to indicate fluid flows through theheat exchangers (e.g., condenser 4020, evaporator 4040), and should beunderstood as not specifying specific flow paths for the fluid flowsthrough the heat exchangers. Dashed and dotted lines are provided in theFigures to illustrate electronic communications between differentfeatures. For example, a dashed dotted line extends between atemperature sensor 4080 and a controller 4070 as the controller 4070receives temperatures readings from the temperature sensor 4080. Forexample, a dashed dotted line extends from the controller 4070 to theheat source 4050 as the controller 4070 can provide energy and/orelectronically control the heat source 4050 in an embodiment.

Working fluid in a lower pressure gaseous state is drawn into thesuction inlet 4012 of the compressor 4010. In an embodiment, thecompressor 4010 is a screw compressor or a scroll compressor. A screwcompressor utilizes one or more rotating screws to compress a gas.Trapped spaces are formed along the blades of the screw(s) as the screwrotates. As the screw(s) rotate, a trapped space is moved along a lengthof the screw and becomes smaller. Gas in the trapped space is compressedas the trapped space becomes smaller. The trapped space eventuallyrotates along an opening and is released as compressed gas. A scrollcompressor includes at least one pair of scrolls. Each scroll includes abaseplate and a wrap, and the wraps of the pair of scrolls areintermeshed. One or both of the scrolls are moved such that the scrollsorbit/rotate relative to each other. As the scrolls orbit/rotaterelative to each other, a trapped space between the intermeshed wrapsand the baseplates is moved along the intermeshed wraps in a clockwiseor counter-clockwise direction and becomes smaller. The gas in thetrapped space is compressed as the trapped space becomes smaller. Thetrapped space eventually reaches an outlet located along a diameter orcentral location of the baseplates and is released as compressed gas.

In an embodiment, the lubricant for the bearings 4016 of the compressor4010 may be provided with the working fluid via the suction inlet 4012of the compressor 4010. In such an embodiment, the compressor 4010 mayalso be a different type of compressor than a screw or scrollcompressor.

The working fluid is compressed as it flows from the suction inlet 4012to an outlet 4014 of the compressor 4010. The compression of the workingfluid in the compressor 4010 also increases the temperature of theworking fluid. Thus, the compressed working fluid discharged from theoutlet 4014 of the compressor has a higher temperature. The compressor4010 utilizes a lubricant to lubricate its moving parts (e.g., rotor,bearings 4016). Lubricant mixes with the working fluid flowing throughthe compressor 4010 such that the compressed working fluid dischargedfrom the compressor 4010 contains lubricant.

In an embodiment, the high pressure and temperature working fluid flowsfrom the outlet 4014 of compressor 4010 to the lubricant separator 4060.The working fluid discharged from the compressor 4010 includes a gaseousportion and a liquid portion. The gaseous portion of the working fluidcontains gaseous refrigerant. The gaseous portion of the working fluidmay also contain entrained lubricant. The liquid portion containslubricant and refrigerant dissolved in the lubricant. The gaseous andliquid portions of the working fluid may also include one or moreadditional components, respectively, as discussed above. The lubricantseparator 4060 is configured to physically separate the gaseous workingfluid from the liquid lubricant. A primary lubricant flow path 4062fluidly connects the lubricant separator 4060 to the compressor 4010.The liquid lubricant is separated in the lubricant separator 4060. Theseparated liquid lubricant then flows back to the compressor 4010 fromthe lubricant separator 4060 through the primary lubricant flow path4062. In an embodiment, the separated lubricant is provided to thebearings 4016 of the compressor 4010.

The higher pressure and temperature gaseous working fluid flows from thelubricant separator 4060 to and through the condenser 4020. A firstprocess fluid PF₁ also separately flows through the condenser 4020. Thecondenser 4020 is a heat exchanger that allows the working fluid and thefirst process fluid PF₁ to be in a heat transfer relationship within thecondenser 4020 without physically mixing. As the working fluid and firstprocess fluid PF₁ flow through the condenser 4020, the working fluid iscooled by the first process fluid PF₁. The process fluid PF₁ is heatedby the working fluid and exits the condenser 4020 at a highertemperature. In an embodiment, the first process fluid PF₁ may be air,water and/or glycol, or the like that is suitable for absorbing andtransferring heat from the working fluid and the heat transfer circuit4001. For example, the first process fluid PF₁ may be ambient aircirculated from an outside atmosphere, water to be heated as hot water,or a fluid for transferring heat from the heat transfer circuit 4001.The working fluid becomes liquid or mostly liquid as it is cooled in thecondenser 4020.

The liquid/gas working fluid flows from the condenser 4020 to theexpansion device 4030. The expansion device 4030 allows the workingfluid to expand. The expansion causes the working fluid to significantlydecrease in temperature. In an embodiment, the expansion device 4030 maybe an expansion valve, expansion plate, expansion vessel, orifice, thelike, or other such types of expansion mechanisms. It should beappreciated that the expansion device 4030 may be any type of expanderused in the field for expanding a working fluid causing the workingfluid to decrease in temperature.

The lower temperature gaseous/liquid working fluid then flows from theexpansion device 4030 to and through the evaporator 4040. A secondprocess fluid PF₂ also flows through the evaporator 4040 separately fromthe working fluid. The evaporator 4040 is a heat exchanger that allowsthe working fluid and the second process fluid PF₂ to be in a heattransfer relationship within the evaporator 4040 without physicallymixing. As the working fluid and second process fluid PF₂ flow throughthe evaporator 4040, the working fluid absorbs heat from the secondprocess fluid PF₂ cooling the second process fluid PF₂. In anembodiment, the evaporator 4040 may be a flooded evaporator as describedbelow with respect to FIG. 15. In an embodiment, the working fluidexiting the evaporator 4040 may be at or about its saturationtemperature.

In an embodiment, the second process fluid PF₂ is air cooled by theHVACR system and ventilated to the enclosed space to be conditioned. Inan embodiment, the second process fluid PF₂ may be an intermediate fluid(e.g., water, heat transfer fluid, or the like) and the cooled secondprocess fluid PF₂ may then be utilized by the HVACR system to cool air.The working fluid is mostly gaseous as it exits the evaporator 4040.

In some embodiments, lubricant that was entrained in gaseous workingfluid exiting the lubricant separator 4060 is later separated due to thetemperature and/or pressure changes of the working fluid as it flows toand/or through the evaporator 4040. This separated lubricant may flow toa bottom of the evaporator 4040. In an embodiment, an optional secondarylubricant flow path 4064 may fluidly connect the evaporator 4040 to thecompressor 4010 and allow the liquid lubricant in the evaporator 4040 toflow back to the compressor 4010.

The mostly gaseous working fluid flows from the evaporator 4040 to andthrough the heat source 4050. The heat source 4050 further heats theworking fluid. The heat source 4050 heats the working fluid to increasethe superheat of the working fluid. Superheat is a measure of thetemperature change relative to the temperature at which the workingfluid evaporates at a set pressure (e.g.,T(P_(x))_(superheat)=T(P_(x))_(Actual)−T(P_(x))_(Saturation)). Forexample, increasing superheat of the working fluid is an increase in thetemperature of the working fluid to above the saturation temperature atwhich the refrigerant(s) of the working fluid change state from a liquidto vapor.

In an embodiment, the heat source 4050 in FIG. 11 is an electrical heatsource that generates heat from supplied electricity. A suction pipe4018 extends from outlet of the evaporator 4040 to the suction inlet4012 of the compressor 4010. In an embodiment, the suction pipe 4018 mayinclude one or more sections or portions (i.e. not be a singlecontinuous length of pipe). In an embodiment, the heat source 4050contacts an outside surface of the suction pipe 4018. In such anembodiment, the heat source 4050 may be wrapped around the suction pipe4018. In an embodiment, the heat source 4050 may be located within thesuction pipe 4018. The heat source 4050 being disposed outside of thesuction pipe 4018 may be advantageous as the heat source 4050 is notlocated in the flow path of the working fluid and can avoid causing apressure drop.

The flow path of the working fluid through the heat circuit 4001includes a suction stream. The suction stream is disposed after thelocation where the working fluid is heated by the second process fluidPF₂ and before the compressor 4010. In an embodiment, the suction streamextends from a location after where the working fluid is heated by thesecond process fluid PF₂ to the suction inlet 4012 of the compressor4010. In an embodiment, the suction stream extends from the evaporator4040 to the suction inlet 4012 of the compressor 4010. In FIG. 11, thesuction stream includes the heat source 4050 and the suction pipe 4018.In an embodiment, the heat transfer circuit 4001 may include additionalcomponents (one or more pipes, flow control device(s), a receiver tank,a dryer, or the like) disposed between the evaporator 4040 and thecompressor 4010. In such an embodiment, the suction stream may alsoinclude such additional components. The heat source 4050 is configuredto provide heat to and increase the temperature of the working fluidflowing through the suction stream (i.e. increase the suctiontemperature T₁).

The temperature of the working fluid entering the compressor 4010(“suction temperature T₁”) is increased by the heat source 4050. Theheat source 4050 increases the temperature of the working fluid as itflows through the suction stream. The increase of the suctiontemperature T₁ causes an increase in a temperature T₂ of the compressor4010 itself and the temperature T₃ of the working fluid exiting thecompressor 4010 (“discharge temperature T₃”).

As discussed above, the working fluid discharged from the compressor4010 includes liquid lubricant. The lubricant is circulated back to thecompressor 4060. In FIG. 11, the lubricant is separated in the lubricantseparator 4060 and separately circulated back to the compressor 4010(e.g., through primary lubricant flow path 4062). However, the heattransfer circuit 4001 in an embodiment may not include the lubricantseparator 4060. In an embodiment, the lubricant may be configured to becirculated back to the compressor 4010 as part of the working fluidwithout being separated with a lubricant separator 4060. In such anembodiment, the lubricant may enter through the suction inlet 4012 ofthe compressor 4010 as part of the working fluid.

As discussed above, the lubricant may contain dissolved refrigerant thatdecreases the lubricity of the lubricant, which has a negative impact onthe efficiency of the compressor 4010 and the heat transfer circuit4001. Additionally, the separated lubricant is at a higher pressureafter the lubricant separator 4060 in FIG. 11. As discussed above, theworking fluid is compressed as it flows through the compressor 4010 fromthe suction inlet 4012 to the outlet 4014. For example, the workingfluid has its highest pressure at the outlet 4014 of the compressor4010. The lubricant may be provided to the compressor 4010 at a locationbefore the outlet 4014. Accordingly, the lubricant undergoes a pressuredrop as it goes from a higher pressure to a lower pressure. The pressuredrop liberates at least some of the refrigerant dissolved in thelubricant. The liberation of the refrigerant in the lubricant allows therefrigerant to expand and thereby cool the lubricant. This temperaturedecrease of the lubricant further decreases the lubricity of thelubricant, reducing and/or countering the increased lubricity caused bythe lubricant having a lower concentration of refrigerant.

The increase in the temperature T₂ of the compressor 4010 increases thetemperature of the lubricant flowing through the compressor 4010. Thiscan reduce and/or counter the temperature decrease caused by therefrigerant being liberated due to the pressure drop. Accordingly, thelubricant has a decreased concentration of refrigerant due to thepressure drop while no longer having a reduced temperature due to theliberation of refrigerant caused by the pressure drop. Thisadvantageously reduces and/or prevents the lowered lubricity caused bydissolved refrigerant while also reducing and/or preventing atemperature decreased that also decreases the lubricity of thelubricant.

The concentration of refrigerant in the lubricant separated in thelubricant separator 4060 is based on temperature and pressure. A highertemperature causes a lower concentration of refrigerant to be dissolvedin the lubricant. Thus, an increase in the discharge temperature T₃ ofthe working fluid results in the separated lubricant having a lowerconcentration of refrigerant. The increased discharge temperature T₃causes the separated lubricant supplied back to the compressor 4010 fromthe lubricant separator 4060 to advantageously have an increasedviscosity and lubricity due to its lower concentration of refrigerant.

The heat transfer circuit 4001 includes a circuit controller 4070 thatcontrols the heat output of the heat source 4050. In an embodiment, thecircuit controller 4070 controls a heat output of the heat source 4050based on at least one of the suction temperature T₁, the dischargetemperature T₃, and/or a temperature of the second process fluid PF₂after the passing through the evaporator 4040 (“second process fluidexit temperature T₄”). In an embodiment, a desired temperature for thesecond process fluid exit temperature T₄ may be at or about 10° F. to ator about 75° F. In an embodiment, a desired temperature for the secondprocess fluid exit temperature T₄ may be at or about 44° F. In anembodiment, the circuit controller 4070 may be an HVACR controller forcontrolling operation of the HVACR system.

In an embodiment, the circuit controller 4070 may control the heatprovided by the heat source 4050 to the working fluid so that thesuction temperature T₁ is within a desired temperature range. In anembodiment, the heat transfer circuit 1 may be configured so that theworking fluid entering the suction inlet 4012 contains the lubricant forlubricating the compressor 4010. For example, a desired temperaturerange for the suction temperature T₁ in an embodiment may be based onone or more of a chemical degradation temperature of the lubricant, aminimum efficiency for the compressor 4010, and/or the concentration oflubricant in the liquid portion of the working fluid entering thesuction inlet 4012. In an embodiment, the desired temperature for thesuction inlet temperature T₁ may be at or about 0° F. to at or about 70°F. In an embodiment, the desired temperature for the suction inlettemperature T₁ may be at or about 40° F. In an embodiment, the superheatof the working fluid entering the compressor 4010 may be at least 6° F.(e.g., T₁−T_(sat)≥6° F.). In an embodiment, the superheat of the workingfluid entering the compressor 4010 may at or about 6° F. to at or about15° F. (e.g., 15° F.≥(T₁−T_(sat))≥6° F.).

In an embodiment, the circuit controller 4070 may control the heatoutput of the heat source 4050 so that the discharge temperature T₃ iswithin a desired temperature range. For example, a desired temperaturerange for the discharge temperature T₃ may be based on one or more of achemical degradation temperature of the lubricant, a minimum efficiencyfor the compressor 4010, and/or a concentration of the lubricant in theliquid portion of the working fluid discharged from the compressor 4010.In an embodiment, a desired temperature for the discharge temperature T₃may be at or about 60° F. to at or about 180° F. In an embodiment, adesired temperature for the discharge temperature T₃ may be at or about125° F. In an embodiment, the discharge temperature T₃ may be controlledso that the separated lubricant provided to the bearings 4016 has alubricant concentration of 70% or greater.

The circuit controller 4070 in FIG. 11 utilizes a sensor 4080 to detectthe suction inlet temperature T₁, a sensor 4082 to detect the dischargetemperature T₃, a sensor 4084 to detect the second process fluid exittemperature T₄, and a sensor 4086 to detect the temperature T₂ of thecompressor 4010. In an embodiment, the heat transfer circuit 4001 mayinclude one or more sensors (e.g., sensor 4080, sensor 4082, sensor4084, sensor 4086, or the like) as suitable and/or desired forcontrolling the heat source 4050 to provide the desired amount of heatto the working fluid as discussed above.

FIG. 12 is a schematic diagram of a heat transfer circuit 4100 accordingto an embodiment. In an embodiment, the heat transfer circuit 4100 maybe employed in an HVACR system. The heat transfer circuit 4100 issimilar to the heat transfer circuit 4001 in FIG. 11, except withrespect to a heat source 4150 and the flow of working fluid between thelubricant separator 4160 and the condenser 4120. For example, the heattransfer circuit 4100 includes a compressor 4110, the optional lubricantseparator 4160, the condenser 4120, an expansion device 4130, and anevaporator 4140. The condenser 4120 utilizes a first process fluid PF₁to cool the working fluid, and the evaporator 4140 utilizes the workingfluid to cool a second process fluid PF₂ similar to the heat transfercircuit 4001 in FIG. 11. In an embodiment, the evaporator 4140 may be aflooded evaporator as described below with respect to FIG. 15. In anembodiment, the working fluid exiting the evaporator 4140 may be at orabout its saturation temperature.

The heat source 4150 is configured to increase the suction temperatureT₁ of the working fluid entering the compressor 4110 similar to the heatsource 450 in FIG. 11. As shown in FIG. 12, the heat source 4150 is aheat exchanger with a first side 4152 and a second side 4154. It shouldbe understood that “side” refers to a separate flow passageway throughthe heat source 4150, and not to a particular physical orientation.Fluids in the first side 4152 and second side 4154 of the heat source4150 exchange heat but do not mix. Working fluid from the evaporator4140 flows to the heat source 4150, through the first side 4152, andfrom the heat source 4150 to the compressor 4110. A first passageway4156 and second passageway 4158 extend from opposite ends of the secondside 4154. A portion of the compressed working fluid exiting thelubricant separator 4160 flows into the first passageway 4156, throughthe second side 4154 of the heat source 4150, through the secondpassageway 4158, and to the condenser 4120. A second portion of thecompressed working fluid exits the lubricant separator 4160, flows pastthe first and second passageways 4156, 4158, and to the condenser 4120.The end 4159 of the second passageway 4158 opposite to the heat source4150 is fluidly connected downstream of the end 4157 of the firstpassageway 4156 opposite to the heat source 4150.

In FIG. 12, the first passageway 4156 and second passageway 4158 areconnected between the lubricant separator 4160 and the condenser 4120.However, the first passageway 4156 and/or the second passageway 4158 inan embodiment may be connected at a different location than shown inFIG. 12. In an embodiment, the first passageway 4156 may be connectedbetween the compressor 4110 and the expansion device 4130. In anembodiment, the first passageway 4156 may be connected between thecompressor 4110 and the lubricant separator 4160. In another embodiment,the first passageway 4156 may be connected between the condenser 4120and the expansion device 4130. In such an embodiment, a portion of thecompressed working fluid discharged from the compressor 4110 would flowfrom the lubricant separator 4160, through the condenser 4120, throughthe heat source 4150, then enter then expansion device 4130.

In an embodiment, the second passageway 4158 may be connected at adifferent location. In an embodiment, the second passageway 4158 may beconnected between the condenser 4120 and the expansion device 4130. Inan embodiment, the second passageway 4158 may be connected between theexpansion device 4130 and the evaporator 4140, and may include a secondexpansion device to provide an expansion to the working fluid flowingthrough the second passageway 4158 similar to the expansion device 4130.In an embodiment, the portion of compressed working fluid may flow fromthe heat source 4050, through the second expansion device, and to theevaporator 4140, bypassing the expansion device 4130. In suchembodiments, the compressed working fluid flowing through the heatsource 4050 may bypass one or both of the condenser 4120 and theexpansion device 4130.

As discussed above, the working fluid increases in temperature as theworking fluid is compressed in the compressor 4110. Accordingly, theworking fluid discharged from the compressor 4110 has a highertemperature and pressure. The heat source 4150 utilizes the highertemperature compressed working fluid to heat the working fluid flowingfrom the evaporator 4140 to the compressor 4110. Utilizing thecompressed working fluid in the heat source 4150 may be advantageous asthe heat source 4150 does not require additional heat (e.g., heatgenerated from electricity, heat provided by an external process fluidor fluid circuit) to be added to the heat transfer circuit 4100.

The heat transfer circuit 4100 includes a circuit controller 4170. Acontrol valve 4155 regulates the flow rate of the compressed workingfluid through the second side 4154 of the heat source 4150. The circuitcontroller 4170 controls the heat provided to the working fluid flowingthrough the first side 4152 of the heat source 4150 using the controlvalve 4155. In an embodiment, the circuit controller 4170 may be anHVACR controller of the HVACR system.

The amount of heat provided to the working fluid flowing through theheat source 4150 may be controlled in a similar manner as discussedregarding the heat source 4050 in FIG. 11. For example, the circuitcontroller 4170 may control the amount of heat provided to the workingfluid flowing through the first side 4152 of the heat source 4150 basedon at least one of the suction temperature T₁, the discharge temperatureT₃, and/or the second process fluid exit temperature T₄. In anembodiment, the heat transfer circuit 4100 may include one or moresensors (e.g., sensor 4180, sensor 4182, sensor 4184, sensor 4186, andthe like) as suitable and/or desired for the heat source 150 to providethe desired amount of heat to the working fluid as discussed above.

The heat source 4150 in FIG. 12 is an active system. However, it shouldbe appreciated that the heat source 4150 in FIG. 12 may be configured asa passive system. In an embodiment, heat transfer circuit 4100 may beconfigured so that the working fluid exits the evaporator 4140 within aset temperature range, and the flow rate of compressed working fluidthrough the heat source 4150 is a set amount or within a set range sothat the working fluid reaches a desired temperature (e.g., suctiontemperature T₁ is above a desired temperature) as discussed above.

The heat source 4150 in FIG. 12 utilizes the compressed working fluid.However, it should be appreciated that the heat source 4150 may utilizea different fluid to heat the working fluid flowing through the firstside 4152 instead of the compressed working fluid. In an embodiment, theheat source 4150 may utilize the first process fluid PF₁, the secondprocess fluid PF₂, or a third process fluid (e.g., hot air, hot water,or the like) that flows through the second side 4154 to heat the workingfluid. In an embodiment, a portion of the second process fluid PF₂,before entering the evaporator 4140, may flow through the second side4154 of the heat source 4150 instead of the compressed working fluid.The portion of the second process fluid PF₂ may then flow through theevaporator 4140 or bypass the evaporator 4140 before joining the rest ofthe second process fluid PF₂. In another embodiment, the first processfluid PF₁ (or a portion of the first process fluid PF₁) after beingheated in the condenser 120 may flow through the second side 4154 of theheat source 4150 instead of the compressed working fluid.

In FIG. 12, the lubricant is separated in the lubricant separator 4160and separately circulated back to the compressor 4110. However, the heattransfer circuit 4100 in an embodiment may not include the lubricantseparator 4160. In an embodiment, the lubricant may be configured to becirculated back to the compressor 4010 as part of the working fluidwithout being separated with a lubricant separator 4060. In such anembodiment, the lubricant may enter through the suction inlet 4012 ofthe compressor 4010 as part of the working fluid.

The flow path of the working fluid through the heat circuit 4100includes a suction stream. The suction stream is disposed after thelocation where the working fluid is heated by the second process fluidPF₂ and before the compressor 4110. In an embodiment, the suction streamextends from a location after where the working fluid is heated by thesecond process fluid PF₂ to the suction inlet 4112 of the compressor4110. In an embodiment, the suction stream extends from the evaporator4140 to the suction inlet 4112 of compressor 4110. In FIG. 12, thesuction stream includes the heat source 4150, the pipe that fluidlyconnects the evaporator 4140 to the heat source 4150, and the suctionpipe that fluidly connects the heat source 4150 to the suction inlet4112 of the compressor 4110. In an embodiment, the heat transfer circuit4100 may include additional components (one or more pipes, flow controldevice(s), a receiver tank, a dryer, or the like) disposed between theevaporator 4140 and the compressor 4110. In such an embodiment, thesuction stream may also include such additional components. The heatsource 4150 is configured to provide heat to and increase thetemperature of the working fluid flowing through the suction stream(i.e. increase the suction temperature T₁).

FIG. 13 is a schematic diagram of a heat transfer circuit 4200 accordingto an embodiment. In an embodiment, the heat transfer circuit 4200 maybe employed in an HVACR system. The heat transfer circuit 4200 issimilar to the heat transfer circuit 4100 in FIG. 12, except withrespect to fluid utilized by the heat source 4250 for heating theworking fluid. For example, the heat transfer circuit includes acompressor 4210, an optional lubricant separator 4260, a condenser 4220,an expansion device 4230, an evaporator 4240, and a circuit controller4270.

Similar to the heat transfer circuit 4100, the flow path of the workingfluid through the heat circuit 4100 includes a suction stream. Thesuction stream is disposed after the location where the working fluid isheated by the second process fluid PF₂ in the evaporator 240 and beforethe compressor 4110. The suction stream includes the heat source 4250.The heat source 4250 is disposed in the suction stream between theevaporator 4240 and the compressor 4210. The heat source 4250 isconfigured to heat the gaseous or mostly gaseous working fluid as itflows from the evaporator 4240 to the compressor 4210.

The heat source 4250 is a heat exchanger that includes a first side 4252and a second side 4254. The working fluid from the evaporator 4240 flowsto the heat source 4250, through the first side 4252, and from the heatsource 4250 to the compressor 4210. The heat source 4250 is fluidlyconnected to a secondary cooling circuit 4290. In an embodiment, thesecondary cooling circuit 4290 may be for cooling electronics. Forexample, the electronics may be the electronics of the compressor 4210or an HVACR system of the heat circuit 4200. The secondary coolingcircuit 4290 utilizes a working fluid to provide cooling. The workingfluid provides cooling by absorbing heat. The working fluid of thesecondary cooling circuit 4290 is provided to the heat source 4250 as athird process fluid. In an embodiment, the third process fluid may beand/or include air, water, refrigerant(s), or the like. The thirdprocess fluid has an elevated temperature as it absorbs heat to providecooling in the secondary cooling circuit 4290. The third process fluidhaving a temperature sufficient for superheating the working fluidflowing through the heat source 4250.

A first passageway 4256 and a second passageway 4258 extend fromopposite ends of the second side 4254 and fluidly connect the secondside 4254 of the heat source 4250 to the secondary cooling circuit 4290.The third fluid flows from secondary cooling circuit 4290 into the firstpassageway 4256, through the second side 4254 of the heat source 4250,through the second passageway 4258, and back to secondary coolingcircuit 4290. As similarly discussed above regarding the heat source4150 in FIG. 12, the third fluid flowing through the second side 4254 isconfigured to superheat the gaseous or mostly gaseous working fluid asit flows through the heat source 4250.

The heat transfer circuit 4200 may include a control valve 4255regulates the flow rate of the third fluid through the second side 4254of the heat source 4250. In a similar manner as discussed aboveregarding the circuit controller 4170 in FIG. 12, the circuit controller4270 may control the heat provided to the working fluid flowing throughthe first side 4252 of the heat source 4250 using the control valve4255. In an embodiment, the circuit controller 4270 may be an HVACRcontroller of the HVACR system. In another embodiment, the heat transfercircuit 4200 may be a passive system as similar discussed above and maynot include/utilize the control valve 4255.

FIG. 14 is a schematic diagram of a heat transfer circuit 4300 accordingto an embodiment. In an embodiment, the heat transfer circuit 4300 maybe employed in an HVACR system. The heat transfer circuit 4300 issimilar to the heat transfer circuit 4100 in FIG. 12, except withrespect to the heat source 4350. For example, the heat transfer circuit4300 includes a compressor 4310, an optional lubricant separator 4360, acondenser 4320, an expansion device 4330, and an evaporator 4340.

The evaporator 4340 includes an inlet 4342 and an outlet 4344. FIG. 15shows a diagram of the flow of the working fluid through the evaporator4340 in an embodiment. The working fluid from the expansion device 4330enters the evaporator 4340 through the inlet 4342 and exits theevaporator 4340 through the outlet 4344. FIG. 15 illustrates anexemplary flow path FP of the working fluid through the evaporator 4340.The working fluid flows from the inlet 4342 of the evaporator 4340, pasta set of heat exchanger tubes 4346, past the heat source 4350, and thento the outlet 4344 of evaporator 4340. The heat exchanger tubes 4346 areconfigured to evaporate the liquid working fluid. The heat source 4350is configured to provide additional heat to the evaporated (or mostlyevaporated) working fluid to superheat the working fluid. In anembodiment, the evaporator 4340 may be a flooded heat exchanger. In suchan embodiment, the liquid working fluid pools in the bottom of theevaporator 4340, and some of the heat exchanger tubes 4346 extendthrough the pool of liquid working fluid. For example, as shown in FIG.15, an upper surface 4353 of the pooled working fluid in the evaporator4340 may be above all of the heat exchanger tubes 4346. Duringoperation, location of the upper surface 4353 (e.g., level) of thepooled working fluid may vary. For example, the upper surface 4353 maylower such that some of the heat exchanger tubes 4346 are not submergedin the pooled liquid working fluid.

The second process fluid PF₂ flows through the heat exchanger tubes4346. The second process fluid PF₂ is configured to heat the pooledliquid working fluid in the evaporator 4340 and continuously evaporatethe liquid working fluid. Once evaporated, the working fluid flowstowards the outlet 4344. In an embodiment, the heat exchanger tubes 4346are configured to heat the working fluid to at or about its saturationtemperature as the heat exchanger tubes 4346 provide a sufficient amountof heat to evaporate the liquid working fluid.

As shown in FIG. 15, the heat source 4350 in an embodiment is anotherset of heat exchanger tubes 4351. The first passageway 4356 is fluidlyconnected to the inlets of the heat exchanger tubes 4351 and the secondpassageway 4358 is fluidly connected to the outlets of the heatexchanger tubes 4351. The passageways 4356, 4358 allow a portion of thecompressed working discharged by the compressor 4310 to pass through theheat exchanger tubes 4351 before the compressed working fluid flows tothe condenser 4320 and the expansion device 4330.

The process fluid PF₂ flows through the heat exchanger tubes 4346. Thecompressed working fluid flows through the next set of heat exchangertubes 4351. In an embodiment, the set of heat exchanger tubes 4351 arespaced apart from the set of heat exchanger tubes 4346. For example, asshown in FIG. 15, a space (e.g., an open space) may be provided betweenthe set of heat exchanger tubes 4346 and the set of heat exchanger tubes4351 along the flow path 4351 of the working fluid. The working fluid isheated as it flows past the heat exchanger tubes 4346 and absorbs heatfrom the flowing process fluid PF₂. The heat exchanger tubes 4346configured to evaporate the liquid working fluid. The heated workingfluid is then heated further as it flows past the heat exchanger tubes4351 and absorbs heat from the compressed working fluid. The heatexchanger tubes 4351 are configured to heat the gaseous or mostlygaseous working fluid. For example, the heat exchanger tubes 4351 areconfigured to be above the upper surface 4353 of the working fluid(e.g., not be submerged in liquid working fluid) during normal operationof the evaporator 4340.

As shown in FIG. 14, the heat transfer circuit 4300 includes a circuitcontroller 4370. The amount of heat provided by the heat source 4350 tothe working fluid flowing past the heat exchanger tubes 4351 iscontrolled by the circuit controller 370 in a similar manner asdiscussed above regarding the heat source 4050 in FIG. 11. For example,the circuit controller 4370 may control the amount of heat provided bythe heat source 4350 to the working fluid flowing past the heatexchanger tubes 4351 based on at least one of the suction temperatureT₁, the discharge temperature T₃, and/or the second process fluid exittemperature T₄. The circuit controller 4370 controls the heat providedby the heat source 4350 using the control valve 4355 to adjust the flowrate of compressed working fluid through the heat exchange tubes 4351.

As shown in FIG. 14, the evaporator 4340 includes a temperature sensor4388. The temperature sensor 4388 is configured to detect a temperatureof the working fluid as it exits the evaporator 4340 (“evaporator outlettemperature T₅”). The heat transfer circuit 4300 in FIG. 14 does notinclude any components that heat or cool the working fluid between theevaporator 4340 and the compressor 4310. Accordingly, the suctiontemperature T₁ would be the same as the evaporator outlet temperatureT₅, and the sensor 4388 may be for detecting the suction temperature T₁instead of sensor 4380. In an embodiment, the heat transfer circuit 4300may include one or more sensors (e.g., sensor 4380, sensor 4382, sensor4384, sensor 4386, sensor 4388, or the like) as suitable and/or desiredfor controlling the heat source 4350 to generate the desired heat outputas discussed above.

The heat source 4350 in the heat transfer circuit 4300 is an activesystem. However, it should be appreciated that the heat transfer circuit4300 and the heat source 4350 may be configured to be a passive systemas similarly discussed above regarding the heat transfer circuit 4100 inFIG. 12. In such an embodiment, circuit controller 4370 may not activelyoperate the heat output of the heat source 4350.

In an embodiment, the passageways 4356, 4358 are connected to the flowpath of the working fluid between the lubricant separator 4360 and thecondenser 4320. However, one or both of the passageways 4356, 4358 maybe connected at a different location than shown in FIG. 14 as similarlydiscussed above regarding the passageways 4156, 4158 in FIG. 12. In anembodiment, the passageways 4356, 4358 are connected after thecompressor 4310 and before the expansion device 4330.

The heat source 4350 in FIGS. 14 and 15 is the heat exchanger tubes 4351through which the compressed working fluid flows. However, the hot fluidflowing through the heat source 4350 in an embodiment may be the firstprocess fluid PF₁, the second process fluid PF₂, or a third processfluid (e.g., hot water, hot air, fluid from a secondary cooling circuit,or the like) instead of the compressed working fluid as similarlydiscussed above regarding the heat source 4150 in FIG. 12 and the heatsource 4250 in FIG. 13. In such an embodiment, the first passageway 4356and the second passageway 4358 would not be fluidly connected to theflow path of the working fluid.

Different steams of fluid flow through heat exchanger tubes 4346 and theheat exchanger tubes 4351. In an embodiment, the streams of fluidflowing through the heat exchanger tubes 4346 and the heat exchangertubes 4351 may be the same type of fluid. In an embodiment, the type offluid flowing through the heat exchanger tubes 4351 may be the secondprocess fluid PF₂ instead of compressed working fluid. A main stream ofsecond process fluid PF₂ is supplied from a source (e.g., a duct systemof an HVACR, an intermediate heat exchange circuit, or the like) (notshown) to the heat circuit 4300. For example, a portion of the mainstream of second process fluid PF₂ branches off and flows through theheat exchanger tubes 4351 of the heat source 4350. The remaining portionof the main stream of second process fluid PF₂ flows through the heatexchanger tubes 4346. The portion of the main stream of second processfluid PF₂ may rejoin the remaining portion of the main stream after theremaining portion has flowed through the heat exchanger tubes 4346.Alternatively, the portion of the main stream of second process fluidPF₂ may rejoin the remaining portion of the main stream before the heatexchanger tubes 4346, such that both portions flow through the heatexchanger tubes 4346. In another example, the main stream of the secondprocess fluid PF₂ flows through the heat exchanger tubes 4351 and thenflows through the heat exchanger tubes 4346.

In another embodiment, the type of fluid flowing through the heatexchanger tubes 4351 may be the first process fluid PF₁ instead ofcompressed working fluid. The first process fluid PF₁ flowing throughthe condenser 4320 is heated by the compressed working fluid. Forexample, after the first process fluid PF₁ flows through the condenser4320, at least a portion of the heated first process fluid PF₁ flowsthrough the heat exchanger tubes 4351 of the heat source 4350. The firstprocess fluid PF₁ being utilized to transfer heat from the compressedworking fluid to the working fluid flowing past the heat exchanger tubes4351.

In another embodiment, the type of fluid flowing through the heatexchanger tubes 4351 may be a third process fluid instead of thecompressed working fluid. For example, the third process fluid may behot air, hot water, working fluid, or the like. In an embodiment, thethird process fluid may be the fluid for a secondary cooling circuit assimilarly discussed in FIG. 13 (e.g., secondary cooling circuit 4290).For example, the third process fluid of the secondary cooling loop maybe a fluid utilized for transferring heat (e.g., air, water and/orglycol, or the like that is suitable for absorbing and transferringheat) or a working fluid that is expanded to provide cooling (e.g., afluid including one or more refrigerants).

In another embodiment, the heat source 4350 may be an electric heatersimilar to the heat source 4050 in FIG. 11. In such an embodiment, theheat source 4350 utilizes supplied electricity to generate the heatprovided to the passing working fluid instead of utilizing a hot fluid(e.g., the compressed working fluid, the third process fluid). Forexample, the circuit controller 4370 in such an embodiment may controlthe amount of heat provided by the heat source 4350 to the passingworking fluid by controlling the amount of electricity supplied to theheat source 4350.

The flow path of the working fluid through the heat circuit 4300includes a suction stream. The suction stream is disposed after thelocation where the working fluid is heated by the second process fluidPF₂ flowing through the heat exchanger tubes 4346 and before thecompressor 4310. In an embodiment, the suction stream extends from afterthe location where the working fluid is heated by the second processfluid PF₂ to the suction inlet 4312 of the compressor 4310. In anembodiment, the suction stream extends from the heat exchanger tubes4346 to the suction inlet 4312 of the compressor 4310. In FIG. 14, thesuction stream includes the heat source 4350, the portion of theevaporator 4340 after the heat exchanger tubes 4346, and the suctionpipe that fluidly connects the evaporator 4340 to the suction inlet 4312of the compressor 4310. In an embodiment, the heat transfer circuit 300may include additional components (one or more pipes, flow controldevice(s), a receiver tank, a dryer, or the like) disposed between theevaporator 4340 and the compressor 4310. In such an embodiment, thesuction stream would also include such additional components. The heatsource 4350 is configured to provide heat to and increase thetemperature of the working fluid as it flows through the suction stream(i.e. increase the suction temperature T₁).

In FIG. 14, the lubricant is separated in the lubricant separator 4360and separately circulated back to the compressor 4310. However, the heattransfer circuit 300 in an embodiment may not include the lubricantseparator 4360. In an embodiment, the lubricant may be configured to becirculated back to the compressor 4310 as part of the working fluidwithout being separated with a lubricant separator 4360. In such anembodiment, the lubricant may enter through the suction inlet 4312 ofthe compressor 4310 as part of the working fluid.

FIG. 16 is a block diagram of a method of operating a heat transfercircuit 400. For example, the method 4400 may be for operating the heattransfer circuit 4001 in FIG. 11, the heat transfer circuit 4100 in FIG.12, and/or the heat transfer circuit 4300 in FIG. 14. In an embodiment,the heat transfer circuit is employed in an HVACR system. The method4400 starts at 4410.

At 4410, a compressor (e.g., compressor 4010, 4110, 4310) is operated tocompress a working fluid. The temperature of the working fluid increasesas it is compressed in the compressor. The compressed working fluiddischarged from the compressor contains lubricant. In an embodiment, thelubricant is circulated to the compressor separately from the workingfluid and mixes with the working fluid as it passes through thecompressor. In such an embodiment, the method 4400 proceeds to optional4420. At optional 4420, a liquid lubricant is separated from the workingfluid by a lubricant separator (e.g., lubricant separator 4060, 4160,4360). The separated liquid lubricant in some cases contains aconcentration of refrigerant that has been dissolved in the liquidlubricant. The separated liquid lubricant is then circulated back to thecompressor from the lubricant separator. A stream of working fluid,which may contain entrained lubricant, is also discharged from thelubricant separator. The method 4400 then proceeds to 4430.

In another embodiment, the lubricant is circulated with the workingfluid to a suction inlet (e.g., suction inlet 4012 in FIG. 11) of thecompressor without being separated with a lubricant separator (e.g.,lubricant separator 4060, 40160, 4360). In such an embodiment, themethod 4400 proceeds from 4410 to 4430 and does not include optional4420.

At 4430, the compressed working fluid is cooled as it flows through acondenser (e.g., condenser 4020, 4120, 4320). The compressed workingfluid is cooled by a first process fluid (e.g., first process fluid PF₁in FIG. 11, 12, or 14) that separately flows through the condenser. Theworking fluid is partially or entirely condensed as it is cooled in thecondenser. The method 4400 then proceeds to 4440.

At 4440, the working fluid from the condenser is expanded by anexpansion device (e.g., expansion device 4030, 4130, 4330). Theexpansion device allows the working fluid to suddenly expand. Theexpansion causes the working fluid to significantly decrease intemperature. The method 4400 then proceeds to 4450.

At 4450, the expanded working fluid from the expansion device is heatedin an evaporator (e.g., evaporator 4040, evaporator 4140, evaporator4340). A second process fluid (e.g., second process fluid PF₂ in FIG.11, 12, or 14) flows through the evaporator separately from the workingfluid. The working fluid absorbs heat from the second process fluid andis heated as it flows through the evaporator. The second process fluidbeing cooled by the working fluid as it flows through the evaporator.The method 4400 then proceeds to 4460.

At 4460, a heat source (e.g., heat source 4050, heat source 4150, heatsource 4350) heats the working fluid after it has been heated by thesecond process fluid. The heating by the heat source increases thesuction temperature (e.g., suction temperature T₁) of the working fluidas it enters the compressor. The increase in suction temperaturedecreases the concentration of dissolved refrigerant in the lubricantprovided to the compressor. In an embodiment, suction stream includesthe heat source. The suction stream is disposed after the location wherethe working fluid is heated by the second process fluid and before thecompressor. In an embodiment, the suction stream extends from a locationafter where the working fluid is heated by the second process fluid to asuction inlet (e.g., suction inlet 4012, suction inlet 4112, suctioninlet 4312) of the compressor. In an embodiment, the heat source heatsthe working fluid as it flows from the evaporator to the compressor. Insuch an embodiment, the suction stream may include a suction pipe thatconnects the suction inlet of the compressor to at least one of the heatsource and the evaporator. In another embodiment, the heat source islocated within the evaporator and heats the working fluid as to flowsthrough the evaporator after being heated by the second process fluid.In such an embodiment, suction stream may include the portion of theevaporator that is after the heat exchanger tubes of the evaporatorthrough which the second process fluid flows (e.g., heat exchanger tubes4346).

In an embodiment, the method 4400 may be modified based on the heattransfer circuit 4001, heat transfer circuit 4100, heat transfer circuit4200, and/or heat transfer circuit 4300 as shown in FIGS. 11-14 and asdescribed above. For example, the method 4400 in an embodiment mayinclude directing hot fluid (e.g., compressed working fluid, the firstprocess fluid PF₁, the second process fluid PF₂, a third process fluid)through the heat source as similarly described for the heat source 4150in FIG. 12, the heat source 4250 in FIG. 13, and the heat source 4350 inFIGS. 13 and 14.

Aspects:

Any of aspects 1-12 can be combined with any of aspects 13-17. It isunderstood that any of aspects 1-17 can be combined with any otheraspects recited herein.

Aspect 1. A heat transfer circuit, comprising: a compressor forcompressing a working fluid; a condenser for cooling the working fluid;an expansion device for expanding the working fluid; an evaporator forproviding a first heating of the working fluid flowing through theevaporator, the first heating being a heat exchange between the workingfluid and a process fluid flowing through the evaporator, a flow path ofthe working fluid extending from the compressor through the condenser,the expansion device, the evaporator, and back to the compressor, theflow path including a suction stream disposed after the first heatingand before the compressor; and a heat source, the suction streamincluding the heat source and the heat source configured to provide asecond heating of the working fluid.

Aspect 2. The heat transfer circuit of aspect 1, wherein the heat sourceis an electric heater.

Aspect 3. The heat transfer circuit of either one of aspects 1 and 2,wherein the heat source is disposed within the evaporator.

Aspect 4. The heat transfer circuit of either one of aspects 1 and 3,wherein the evaporator includes a first set of heat exchanger tubesthrough which the process fluid flows, and the working fluid flowingpast the first set of tubes undergoing the first heating, and the heatsource is a second set of heat exchanger tubes in the evaporator, thesecond heating of the working fluid being a heat exchange between theworking fluid flowing past the second set of heat exchange tubes and athird fluid flowing through the second set of heat exchanger tubes.

Aspect 5. The heat transfer circuit of either one of aspects 1 and 2,the heat source is disposed in the suction stream between the evaporatorand the compressor.

Aspect 6. The heat transfer circuit of either one of aspects 1 and 5,wherein the heat source is a heat exchanger including a first side and asecond side, the working fluid heated by the heat source flowing throughthe first side, a third fluid flowing through the second side, and thesecond heating of the working fluid being a heat exchange between thethird fluid and the working fluid.

Aspect 7. The heat transfer circuit of either one aspects 4 and 6,wherein the third fluid is a portion of the compressed working fluiddischarged by the compressor before the compressed working fluid flowsthrough the expansion device.

Aspect 8. The heat transfer circuit of either one of aspects 4 and 6,wherein the third fluid is the same type of fluid as the process fluid.

Aspect 9. The heat transfer circuit of either one of aspects 4 and 6,wherein a second process fluid flows through the condenser and absorbsheat from the working fluid to provide the cooling of the working fluid,and the third fluid includes a portion of the second process fluid.

Aspect 10. The heat transfer circuit of either one of aspects 1, 2, 5,and 6, further comprising: a suction pipe extending to a suction inletof the compressor, the suction stream including the suction pipe,wherein the heat source extends along an outside of the suction pipe.

Aspect 11. The heat transfer circuit of any one of aspects 1-10, furthercomprising: a controller configured to control heat provided by the heatsource to the working fluid based on a suction temperature of theworking fluid entering the compressor.

Aspect 12. The heat transfer circuit of any one of aspects 1-11, whereinthe heat source is configured to increase superheat of the working fluidentering a suction inlet of the compressor.

Aspect 13. A method of operating a heat transfer circuit to cool a firstprocess fluid, the heat transfer circuit including a compressor, acondenser, an expansion device, an evaporator, a heat source, and aworking fluid flowing through the heat transfer circuit, the methodcomprising: compressing the working fluid with the compressor; coolingthe working fluid compressed by the compressor with the condenser;expanding the working fluid cooled by the condenser with the expansiondevice; heating the working fluid expanded by the expansion device inthe evaporator with a process fluid, the working fluid absorbing heatfrom the process fluid; and heating the working fluid heated by theprocess fluid with the heat source, the working fluid heated with theheat source as the working fluid flows through a suction stream, thesuction stream including the heat source and disposed after a locationat which the working fluid is heated by the process fluid and before thecompressor.

Aspect 14. The method of aspect 13, wherein heating the working fluidwith the heat source includes heating the working fluid flowing from theevaporator to the compressor.

Aspect 15. The method of either one of aspects 13 and 14, whereinheating the working fluid with the heat source includes increasingsuperheat of the working fluid entering a suction inlet of thecompressor.

Aspect 16. The method of any one of aspects 13-15, further comprising:directing the working fluid from an inlet of the evaporator, past afirst set of heat exchanger tubes in the evaporator through which thefirst fluid flows, past the heat source, and to an outlet of theevaporator in this order, wherein the suction stream includes a portionof the evaporator located after the first set of heat exchanger tubes.

Aspect 17. The method of any one of aspects 13-15, further comprising:directing at least a portion of the compressed working fluid dischargedby the compressor, which has not been expanded by the expansion device,through a first side of the heat source, wherein heating the workingfluid heated by the process fluid with the heat source includesdirecting the working fluid heated by the heat source through a secondside of the heat source.

A heat transfer circuit that utilizes a working fluid to provide heatingor cooling. The heat transfer circuit includes a compressor forcompressing the working fluid and a heat source configured to increase asuction temperature of the working fluid entering the compressor. A flowpath of the working fluid through the heat transfer circuit includes asuction stream. The suction stream is disposed after a location at whichthe working fluid is heated by a process fluid and before thecompressor. The suction stream includes the heat source. A method foroperating a heat transfer circuit includes heating a working fluid witha process fluid, and further heating the working fluid heated by theprocess fluid with a heat source.

Lubricant Management for an HVACR System (FIGS. 17-19)

This disclosure relates generally to a heating, ventilation, airconditioning, and refrigeration (HVACR) system. More specifically, thisdisclosure relates to lubricant management for a compressor in an HVACRsystem.

A heating, ventilation, air conditioning, and refrigeration (HVACR)system includes a refrigerant circuit. The refrigerant circuit includesa compressor, lubricant source, a condenser, an expansion device, and anevaporator fluidly connected. One or more sensors are included fordetermining a pressure and a temperature. The compressor includes aplurality of bearings and a suction port. A lubricant reservoir isfluidly connected to the lubricant source, the plurality of bearings,and the suction port. The lubricant reservoir is configured to receive alubricant-refrigerant mixture. The lubricant reservoir is in thermalcommunication with a discharge flow path of the compressor.

A heating, ventilation, air conditioning, and refrigeration (HVACR)system is also disclosed. The HVACR system includes a refrigerantcircuit. The refrigerant circuit includes a compressor including aplurality of bearings and a suction port, a lubricant source, acondenser, an expansion device, and an evaporator fluidly connected. Oneor more sensors are included for determining a pressure and atemperature. The plurality of bearings include discharge side bearingsand suction side bearings. The plurality of bearings are fluidlyconnected to the lubricant source and configured to receive a lubricantmixture from the lubricant source. The discharge side bearings arefluidly connected to the suction port.

Environmental impacts of HVACR refrigerants are a growing concern. Forexample, since 2011, the European Union has been phasing outrefrigerants with a global warming potential (GWP) of more than, forexample, 150 in some refrigeration systems. Environmentally-suitableHVACR refrigerants, with suitable properties such as density, vaporpressure, heat of vaporization, and suitable chemical properties, whichsatisfy the requirements regarding safety and environment impacts, suchas the European Union standard discussed above, can be utilized forHVACR systems. The environmentally-suitable HVACR refrigerants arenonflammable or mildly flammable, non-ozone depleting, energy efficient,low in toxicity, compatible with materials of construction, and arechemically stable over the life of the equipment.

Current refrigerants, such as R134a or the like, may have relativelyhigher GWPs. For example, R134a has a GWP of 1,430. As a result,replacement refrigerants such as, but not limited to, R1234ze, R513A,and the like, are being implemented in HVACR systems.

In utilizing newer refrigerant compositions such as, but not limited to,R1234ze and R513A, various problems may arise as a result of thedifferent properties of the refrigerant compared to prior refrigerantssuch as R134a. In general, refrigerants with lower GWPs such as R1234ze,R513A, and the like may be carried over into the lubricant. In someinstances, the replacement refrigerants are relatively more likely todissolve into the lubricant than the current refrigerants, resulting ina higher concentration of refrigerant within the lubricant (e.g.,lubricant dilution).

As a result, portions of an operating map for a compressor of the HVACRsystem may suffer from higher lubricant dilution and limited bearingviscosity due to low discharge superheat. In some instances, theoccurrence of higher lubricant dilution and limited bearing viscositymay be more significant when the variable speed compressor operates atrelatively lower speeds. Higher lubricant dilution and limited bearingviscosity can result in, for example, a shortened lifetime for thebearings and ultimately compressor failures. In some instances,utilizing the R134A replacement refrigerants may require a replacementof the mechanical components (e.g., bearings or the like) in thecompressor.

In other instances, controlling a variable speed compressor to maximizeefficiency can also result in lubricant dilution problems, even whenutilizing the current refrigerants such as R134a.

In general, lubricants utilized with R134a replacement refrigerantssuffer the higher lubricant dilution problem. The lubricants can includeany suitable lubricant which is miscible with the selected replacementrefrigerant.

In general, higher lubricant dilution may occur when discharge superheatbecomes relatively low. For example, higher lubricant dilution can occurwhen the discharge superheat is below at or about 8° C.

FIG. 17 is a schematic diagram of a refrigerant circuit 5010, accordingto an embodiment. The refrigerant circuit 5010 generally includes acompressor 5015, a condenser 5020, an expansion device 5025, anevaporator 5030, and a lubricant source 5060.

The refrigerant circuit 5010 is an example and can be modified toinclude additional components. For example, in an embodiment, therefrigerant circuit 5010 can include other components such as, but notlimited to, an economizer heat exchanger, one or more flow controldevices, a receiver tank, a dryer, a suction-liquid heat exchanger, orthe like.

The refrigerant circuit 5010 can generally be applied in a variety ofsystems used to control an environmental condition (e.g., temperature,humidity, air quality, or the like) in a space (generally referred to asa conditioned space). Examples of such systems include, but are notlimited to, HVACR systems, transport refrigeration systems, or the like.

The compressor 5015, condenser 5020, expansion device 5025, andevaporator 5030 are fluidly connected via refrigerant lines 5035, 5040,5045. In an embodiment, the refrigerant lines 5035, 5040, and 5045 canalternatively be referred to as the refrigerant conduits 5035, 5040, and5045, or the like.

In an embodiment, the refrigerant circuit 5010 can be configured to be acooling system (e.g., an air conditioning system) capable of operatingin a cooling mode. In an embodiment, the refrigerant circuit 5010 can beconfigured to be a heat pump system that can operate in both a coolingmode and a heating/defrost mode.

The refrigerant circuit 5010 can operate according to generally knownprinciples. The refrigerant circuit 5010 can be configured to heat orcool a gaseous process fluid (e.g., a heat transfer medium or fluid suchas, but not limited to, air or the like), in which case the refrigerantcircuit 5010 may be generally representative of an air conditioner orheat pump.

In operation, the compressor 5015 compresses a working fluid (e.g., aheat transfer fluid such as a refrigerant or the like) from a relativelylower pressure gas (e.g., suction pressure) to a relativelyhigher-pressure gas (e.g., discharge pressure). In an embodiment, thecompressor 5015 can be a positive displacement compressor. In anembodiment, the positive displacement compressor can be a screwcompressor, a scroll compressor, a reciprocating compressor, or thelike. In an embodiment, the compressor 5015 can be a centrifugalcompressor.

The relatively higher-pressure gas is also at a relatively highertemperature, which is discharged from the compressor 5015 and flowsthrough refrigerant line 5035 to the condenser 5020. The working fluidflows through the condenser 5010 and rejects heat to a process fluid(e.g., water, air, or the like), thereby cooling the working fluid. Thecooled working fluid, which is now in a liquid form, flows to theexpansion device 5025 via the refrigerant line 5040. The expansiondevice 5025 reduces the pressure of the working fluid. As a result, aportion of the working fluid is converted to a gaseous form. The workingfluid, which is now in a mixed liquid and gaseous form flows to theevaporator 5030 via the refrigerant line 5040. The working fluid flowsthrough the evaporator 5030 and absorbs heat from a process fluid (e.g.,water, air, or the like), heating the working fluid, and converting itto a gaseous form. The gaseous working fluid then returns to thecompressor 5015 via the refrigerant line 5045. The above-describedprocess continues while the refrigerant circuit is operating, forexample, in a cooling mode (e.g., while the compressor 15 is enabled).

In the illustrated embodiment, the refrigerant circuit 5010 can includea lubricant source 5060 disposed between the compressor 5015 and thecondenser 5020. In the illustrated embodiment, the lubricant source 5060can be a lubricant separator. It will be appreciated that a particularlocation for the lubricant source 5060 can vary within the principles ofthis disclosure. For example, in an embodiment, the lubricant source5060 could alternatively be a location at or near the evaporator 5030.

The lubricant source 5060 is fluidly connected to a discharge of thecompressor 5015 via the refrigerant line 5035. The lubricant source 5060is fluidly connected to the compressor 5015 to provide lubricant tovarious components of the compressor 5015 (e.g., bearings, rotors, orthe like) via lubricant return line 5055A and optionally via a secondlubricant return line 5055B. It will be appreciated that the number oflubricant return lines 5055A, 5055B can be selected based on, forexample, which components of the compressor are being provided withlubricant.

A controller 5050 is included in the system. The controller 5050 can beused to control one or more aspects of the refrigerant circuit 5010. Forexample, in embodiments disclosed in accordance with FIGS. 18 and 19below, the controller 5050 can be used to selectively control a state ofa flow control device (e.g., a valve or the like) to control lubricantflow within the refrigerant circuit 5010. The controller 5050 can be inelectronic communication with the flow control device and one or moresensors 5065 to determine one or more operating conditions (e.g.,temperature, pressure, or the like) of the compressor 5015 and itscomponents (e.g., bearings, rotors, or the like). In an embodiment, thecontroller 5050 can monitor a pressure and temperature of the lubricantusing the one or more sensors 5065. The controller 5050 will use themeasured pressure and temperature to selectively manage the lubricantflow rate (e.g., to the bearings, the rotors, or the like) to achieve adesired lubricant viscosity. In an embodiment, the pressure may bemeasured in a bearing cavity or inferred from a suction pressure orsuction saturation temperature. In an embodiment, the temperature may bemeasured at the bearings or in a lubricant reservoir.

FIG. 18 is a side sectional view of a compressor 5015 for a vaporcompression system (e.g., the refrigerant circuit 5010 of FIG. 17),according to an embodiment.

In an embodiment, the compressor 5015 is a screw compressor. The screwcompressor 5015 includes a rotor housing 5100 and an electric motorhousing 5105. The rotor housing 5100 includes a suction port 5110 and adischarge port 5115. Rotors 5120 a, 5120 b are intermeshed and aredisposed at least partially within the rotor housing 5100. The screwcompressor 5015 can operate in accordance with generally knownprinciples to compress a working fluid received via the suction port5110 and to be output via the discharge port 5115.

The motor housing 5105 houses a motor 5125, according to an embodiment.The motor housing 5105 may be integral to the rotor housing 5100. Theelectric motor 5125 can drive the intermeshed rotors 4120 a, 4120 b.

The motor housing 4105 includes the electric motor 4125. The motorhousing 4105 further includes a stator 5140 and a rotor 5145. The rotor5145 rotates a shaft which is also connected to the rotor 5120 b. Anairgap 5130 is formed between the stator 5140 and the rotor 5145. In theembodiment illustrated in FIG. 18, the electric motor 5125 can beprovided with a portion of the working fluid (e.g., a heat transferfluid such as refrigerant or the like) which flows through the airgap5130 of the electric motor 5125, in a flow direction which is generallyfrom right to left with respect to the figure, and is provided to thesuction port 5110. In an embodiment, the working fluid can be in agaseous form. It will be appreciated that a gaseous form of the workingfluid may include a portion that is in liquid form, but the gaseous formincludes a relatively higher portion of the working fluid in the gaseousform than the liquid form.

A bearing housing 5135 contains discharge side bearings 5150. Suctionside bearings 5155 are disposed within the rotor housing 5100. Acombination of the discharge side bearings 5150 and the suction sidebearings 5155 support the rotors 5120 a, 5120 b. The discharge sidebearings 5150 and the suction side bearings 5155 can be provided with alubricant for lubricating the discharge side bearings 5150 and thesuction side bearings 5155. In an embodiment, the discharge sidebearings 5150 can include radial bearings and thrust bearings. In anembodiment, a bearing may be configured to accommodate both thrust andradial loads.

In an embodiment, the discharge side bearings 5150 in the bearinghousing 5135 are maintained at a pressure that is lower than a dischargepressure of the compressor 5015. In an embodiment, the discharge sidebearings 5150 in the bearing housing 5135 are maintained at a pressurethat is at or about a suction pressure of the compressor 5015. In anembodiment, the suction side bearings 5155 are also at or about thesuction pressure of the compressor 5015.

In the illustrated embodiment, a lubricant reservoir 5160 is disposed ata location that thermally communicates with the compressor 5015. In anembodiment, the lubricant reservoir 5160 can alternatively be referredto as a lubricant still or a lubricant sump. In an embodiment, theentire lubricant reservoir 5160 or a portion of the lubricant reservoir5160 can be disposed within the rotor housing 5100. In an embodiment,the lubricant reservoir 5160 can be placed at a location that isrelatively closer to the discharge port 5115 than the suction port 5110.As a result, the lubricant reservoir 5160 can receive more heatgenerated through the compression process than if located relativelycloser to the suction port 5110. The thermal communication with thedischarge flow path of the compressor 5015 can include a location atwhich the lubricant reservoir 5160 can receive heat generated from thecompression process. The discharge flow path can include, for example, arotor housing of the compressor 5015, a bearing housing of thecompressor 5015, a muffler of the compressor 5015, a discharge conduitof the compressor 5015, an oil separator, a condenser, or the like. Inan embodiment, the lubricant reservoir 5160 can be in thermalcommunication with another heat generating component of the HVACR systemsuch as, but not limited to, a variable frequency drive controller, anelectric fan motor, or the like.

In an embodiment, a total volume of the lubricant reservoir 5160 can beless than a typical low-side lubricant sump in prior systems. In theillustrated embodiment, the lubricant reservoir 5160 is disposed on atop (with respect to the page) of the compressor 5015. The placement canenable fluid flow from the lubricant reservoir 5160 to the compressor5015 via gravity. As a result, in an embodiment, the lubricant reservoir5160 does not include a pump. This can, for example, reduce a cost andcomplexity of the system relative to prior systems which generallyutilize a pump to move lubricant.

In an embodiment, the lubricant reservoir 5160 can be placed at or nearthe lubricant source 5060 so that the fluid in the lubricant reservoir5160 can receive heat from the higher temperature working fluid at thelocation of the lubricant source 5060.

The lubricant reservoir 5160 is fluidly connected to the lubricantsource 5060. In operation, the lubricant reservoir 5160 can receivelubricant as separated from the lubricant source 5060. Even though thelubricant reservoir 5160 is downstream of the lubricant source 5060, thelubricant can include a mixture of lubricant and refrigerant.

An expansion device 5165 is disposed at a location between the lubricantsource 5060 and the lubricant reservoir 5160. The expansion device 5165can be, for example, a fixed or variable orifice that induces a pressuredrop in the lubricant being received from the lubricant source 5060. Inan embodiment, the expansion device 5165 can be an electronic expansiondevice or the like.

Inducing the pressure drop also reduces a temperature of the lubricantmixture. The mixed refrigerant and lubricant mixture received in thelubricant reservoir 5160 can be heated due to thermal communication witha discharge flow path of the compressor 5015. The thermal communicationwith the discharge flow path of the compressor 5015 can include alocation at which the lubricant reservoir 5160 can receive heatgenerated from the compression process. The discharge flow path caninclude, for example, a rotor housing of the compressor 5015, a bearinghousing of the compressor 5015, a muffler of the compressor 5015, adischarge conduit of the compressor 5015, an oil separator, a condenser,or the like. The heat can cause the refrigerant in the refrigerant andlubricant mixture to boil off to the gaseous state. In an embodiment, anelectric resistance heater could be included, although the electricresistance heater may reduce performance of the compressor 5015.

A conduit 5170 is fluidly connected to a top portion of the lubricantreservoir 5160 so that the gaseous refrigerant boiling from therefrigerant and lubricant mixture can be returned to the suction port5110 of the compressor 5015.

The conduit 5170 includes a flow control device 5175. In an embodiment,the flow control device 5175 can be, for example, a fixed orifice. Theflow control device 5175 in such an embodiment can limit an overallflowrate of the refrigerant flowing from the lubricant reservoir 5160 tothe suction port 5110. In an embodiment, the orifice can be variable. Insuch an embodiment, a size of the orifice can be controlled to controlan amount of flow through the conduit 5170 to the suction port 5110.

In an embodiment, the flow control device 5175 can be a valve. In suchan embodiment, the flow control device 5175 can have a plurality ofstates (e.g., an open state, a closed state, one or more intermediatestates). The state of the flow control device 5175 can be selectivelycontrolled using a controller (e.g., controller 5050, FIG. 17) tocontrol an amount of flow through the conduit 5170.

A second conduit 5180 is fluidly connected to a bottom portion of thelubricant reservoir 5160. The second conduit 5180 is fluidly connectedto the discharge side bearings 150 and the suction side bearings 5155.The second conduit 180 is disposed at a location of the lubricantreservoir 5160 via which a lubricant (e.g., in a liquid or substantiallyliquid state) can flow via, for example, gravity. The lubricant can thenbe provided to the discharge side bearings 5150 and the suction sidebearings 5155.

The flow control device 5175 in the conduit 5170 can be designed so thata flowrate of the lubricant in the conduit 5180 is controlled. Forexample, to increase a lubricant flow to the discharge side bearings5150 and the suction side bearings 5155, the flow control device 175 canbe placed into the closed state by the controller 5050. As a result, apressure in the lubricant reservoir 5160 can increase, thereby resultingin an increased flow of lubricant through the conduit 5180.

The flow control device 5175 can be selectively controlled based on, forexample, a temperature as sensed in the bearing housing 5150.

During operation of the compressor, the discharge side bearings 5150 andthe suction side bearings 5155 generate heat. With focus on thedischarge side bearings 5150, when the heat is generated duringoperation, the lubricant pool is heated. In an embodiment, the dischargeside bearings 5150 can be a flooded bearing design in which drag of thedischarge side bearings 5150 in the lubricant pool can generate heat.The heat can raise a temperature of the lubricant in the cavity of thedischarge side bearings. As the heat increases, lubricant viscosityincreases for a period of time until the heat becomes excessive, atwhich point the lubricant viscosity drops. As discussed above, thelubricant received from the lubricant source 5060 can include a mixtureof lubricant and refrigerant. As a result, when the lubricant pool isheated, refrigerant may be boiled off from the mixture.

When the temperature increases to a threshold limit, indicating thatadditional lubricant is desired, the controller 5050 can place the flowcontrol device 5175 in the closed state, thereby increasing flow oflubricant from the lubricant reservoir 5160 to the discharge sidebearings 5150 and the suction side bearings 5155.

When the temperature is within the threshold limit, indicating thatadditional lubricant is not needed, the controller 5050 can place theflow control device in the open state, thereby decreasing flow oflubricant from the lubricant reservoir 5160 to the discharge sidebearings 5150 and the suction side bearings 5155.

In an embodiment, the flow control device 5175 can include anintermediate state in which some flow is permitted (e.g., between theopen and the closed state). In such an embodiment, the controller 5050can vary the position of the flow control device 5175 to maintain thesensed temperature within a desired operating range.

In an embodiment, by controlling the pressure in the lubricant reservoir5160 to maintain a selected lubricant flowrate to the discharge sidebearings 5150 and the suction side bearings 5155, the lubricantreservoir 5160 may generally be considered to be at a medium pressurethat is between the suction pressure and the discharge pressure of thecompressor 5015.

FIG. 19 is a side sectional view of a compressor 5015 for a vaporcompression system (e.g., the refrigerant circuit 5010 of FIG. 17),according to an embodiment.

For simplicity of this Specification, aspects of FIG. 19 which havepreviously been described with respect to FIG. 18 will not be describedin additional detail. Such aspects are labeled with the same referencenumbers as FIG. 18.

In FIG. 19, the lubricant reservoir 5160 is not present. Instead, thedischarge side bearings 5150 are fluidly connected to the suction port5110. Connecting the discharge side bearings 5150 with the suction port5110 enables refrigerant gas to be returned from the discharge sidebearings 5150 to the suction stream. As a result, refrigerant gas can beremoved from the cavity in which the discharge side bearings 5150 arelocated.

In operation, lubricant is provided to the discharge side bearings 5150and the suction side bearings 5155 via the conduit 5180. A pool oflubricant is formed within the cavity in which the discharge sidebearings 5150 and the suction side bearings 5155 are located.

As discussed above regarding FIG. 18, during operation of thecompressor, the discharge side bearings 5150 and the suction sidebearings 5155 generate heat. With focus on the discharge side bearings5150, when the heat is generated during operation, the lubricant pool isheated. As discussed above, the lubricant received from the lubricantsource 5060 can include a mixture of lubricant and refrigerant. As aresult, when the lubricant pool is heated, refrigerant may be boiled offfrom the mixture. The gaseous refrigerant can be removed from the cavityvia conduit 5200 and lubricant can be removed via conduit 5205. Theconduit 5200 is fluidly connected to the cavity containing the dischargeside bearings 5150 and to the suction port 5110. The conduit 5205 isalso fluidly connected to the cavity containing the discharge sidebearings 5150 and to the suction port 5110. As illustrated, an inlet ofthe conduit 5200 is disposed at a location on a top side of the cavity(e.g., above a depth of the lubricant pool in the cavity) so thatgaseous refrigerant can be removed and the inlet of the conduit 5205 isdisposed at a location on a lower side of the cavity (e.g., below adepth of the lubricant pool in the cavity) so that liquid lubricant canbe removed.

The conduit 5200 can include a flow control device 5210 which can beselectively controlled to enable, disable, or limit the amount ofrefrigerant being pulled from the discharge side bearings 5150 andprovided to the suction port 5110. In an embodiment, the conduit 200 canbe sized to restrict a flow of fluid therethrough to a predeterminedflowrate. When the flow control device 5210 is closed, a pressure in thebearing cavity increases. As the pressure increases, a flow of lubricantfrom the lubricant source 5060 decreases. If the temperature in thecavity approaches an upper limit, the flow through conduit 5200 can beenabled, allowing gaseous refrigerant to leave the cavity and increasinga flow of lubricant from the lubricant source 5060, which should reducea temperature of the discharge side bearings 50150,

The conduit 5205 can include a flow control device 5215. In anembodiment, the flow control device 5215 can be a restriction, such as afixed orifice. In an embodiment, the flow control device 5215 canalternatively be selectively controllable to, for example, vary a flowthrough the conduit 5205. In such an embodiment, the flow control device5215 can be a valve or the like.

In operation, the controller (e.g., controller 5050 in FIG. 17) can beused to monitor a temperature of the lubricant for the discharge sidebearings 5150 (e.g., using one or more sensors 5065). If the temperatureof the lubricant increases beyond a threshold limit, additionallubricant can be provided to the discharge side bearings 5150. If thetemperature decreases below a threshold limit, additional lubricant canbe prevented from being provided.

Aspects:

Any of aspects 1-9 can be combined with any one of aspects 10-17. It isunderstood that any of aspects 1-17 can be combined with any otheraspects recited herein.

Aspect 1. A heating, ventilation, air conditioning, and refrigeration(HVACR) system, comprising: a refrigerant circuit, including: acompressor including a plurality of bearings and a suction port, alubricant source, a condenser, an expansion device, and an evaporatorfluidly connected; one or more sensors for determining a pressure and atemperature; and a lubricant reservoir fluidly connected to thelubricant source, the plurality of bearings, and the suction port, thelubricant reservoir configured to receive a lubricant-refrigerantmixture, wherein the lubricant reservoir is in thermal communicationwith a discharge flow path of the compressor.

Aspect 2. The HVACR system of aspect 1, further comprising a flowcontrol device disposed between the lubricant reservoir and the suctionport.

Aspect 3. The HVACR system of aspect 2, wherein the flow control deviceis one of an orifice and an electronically controlled valve.

Aspect 4. The HVACR system of any one of aspects 1-3, wherein thelubricant reservoir is fluidly connected to the plurality of bearings ata location configured to provide a lubricant to the plurality ofbearings.

Aspect 5. The HVACR system of any one of aspects 1-4, wherein thelubricant reservoir is fluidly connected to the suction port at alocation configured to provide a gaseous refrigerant to the suctionport.

Aspect 6. The HVACR system of any one of aspects 1-5, wherein a pressurewithin the lubricant reservoir is between a suction pressure of thecompressor and a discharge pressure of the compressor.

Aspect 7. The HVACR system of any one of aspects 1-6, wherein a conduitfluidly connecting the lubricant reservoir and the suction port is sizedto restrict a flow of fluid therethrough to a predetermined flowrate.

Aspect 8. The HVACR system of any one of aspects 1-7, wherein thecompressor is a screw compressor.

Aspect 9. The HVACR system of any one of aspects 1-8, wherein thelubricant source is a lubricant separator.

Aspect 10. A heating, ventilation, air conditioning, and refrigeration(HVACR) system, comprising: a refrigerant circuit, including: acompressor including a plurality of bearings and a suction port, alubricant source, a condenser, an expansion device, and an evaporatorfluidly connected; one or more sensors for determining a pressure and atemperature; and wherein the plurality of bearings include a dischargeside bearing and a suction side bearing, the plurality of bearingsfluidly connected to the lubricant source and configured to receive alubricant mixture from the lubricant source, and wherein the dischargeside bearing is fluidly connected to the suction port.

Aspect 11. The HVACR system of aspect 10, further comprising a flowcontrol device disposed between the discharge side bearing and thesuction port.

Aspect 12. The HVACR system of aspect 11, wherein the flow controldevice is one of an orifice and an electronically controlled valve.

Aspect 13. The HVACR system of any one of aspects 10-12, wherein thelubricant mixture includes a lubricant and a refrigerant.

Aspect 14. The HVACR system of any one of aspects 10-13, wherein thefluid connection between the discharge side bearing and the suction portis disposed at a location configured to provide a gaseous refrigerant tothe suction port.

Aspect 15. The HVACR system of any one of aspects 10-14, wherein aconduit fluidly connecting the discharge side bearing and the suctionport is sized to restrict a flow of fluid therethrough to apredetermined flowrate.

Aspect 16. The HVACR system of any one of aspects 10-15, wherein thecompressor is a screw compressor.

Aspect 17. The HVACR system of any one of aspects 10-16, wherein thelubricant source is a lubricant separator.

A heating, ventilation, air conditioning, and refrigeration (HVACR)system includes a refrigerant circuit. The refrigerant circuit includesa compressor, a lubricant source, a condenser, an expansion device, andan evaporator fluidly connected. The compressor includes a plurality ofbearings and a suction port. A lubricant reservoir is fluidly connectedto the lubricant source, the plurality of bearings, and the suctionport. The lubricant reservoir is configured to receive alubricant-refrigerant mixture. The lubricant reservoir is in thermalcommunication with a discharge flow path of the compressor.

Heat Exchanger in Compressor Housing and Method for Degassing CompressorLubricant (FIGS. 20-24)

The disclosure relates to an internal heat exchanger within acompressor, a system, and a method for improving viscosity of alubricant to be recycled back into the compressor for reuse.

The internal heat exchanger is in fluid communication with thecompressor, for example cavities of bearings of the compressor. Theinternal heat exchanger can utilize system heat in the compressor todrive refrigerant out of the lubricant to be recycled back into thecompressor. In an embodiment, the lubricant is oil.

The internal heat exchanger can include a single or a plurality ofpassages. The passage(s), in part or as a whole, can be provided orformed within a component of the compressor or on a surface of acomponent of the compressor. In an embodiment, the passage(s), in partor as a whole, can extend within a component of the compressor. In anembodiment, the passage(s), in part or as a whole, can be integratedinto a component of the compressor. In an embodiment, the passage(s), inpart or as a whole can be formed onto or into a surface of a componentof the compressor. The surface can include, but not limited to, aninterface surface or a face of the component.

The component can be, but not limited to, a bearing housing cover,bearing housing, rotor housing, motor housing, muffler of thecompressor.

The passage(s), in part or as a whole, can be a machined passage(s) orpassage(s).

In an embodiment, the passage(s), in part or as a whole, can bemanufactured through a process including but not limited to drilling,casting, etching, milling, welding, or retrofitting, combinationsthereof, or the like.

In an embodiment, the passage(s), in part or as a whole, can be castedor drilled within a wall of a casting of a bearing housing cover,bearing housing, rotor housing, motor housing, or muffler of thecompressor. Thereby, the casting can utilize system heat to removerefrigerant from the lubricant returning to the compressor.

In an embodiment, the passage(s), in part or as a whole, can be milledon a surface including but not limited to an interface surface or faceof a bearing housing cover, bearing housing, rotor housing, motorhousing, or muffler of the compressor.

The passage(s), in part or as a whole, can adopt any type of suitableflow configuration including but not limited to serpentine, straight,and curved flow configurations.

The passage(s), in part or as a whole, can be configured into any typeof flow arrangements including but not limited to a single-pass ormulti-pass passage. In an embodiment, the single-pass or multi-passpassage can be serpentine single-pass or serpentine multi-pass passages.

In an embodiment, the compressor is a screw compressor. In anembodiment, the compressor is a scroll compressor. In an embodiment, thecompressor is a reciprocating compressor. In an embodiment, thecompressor is a centrifugal compressor.

The system in an embodiment can be an HVACR system including acompressor having an internal heat exchanger. The HVACR system caninclude a lubricant source. In an embodiment, the lubricant source maybe a lubricant separator. The lubricant separator can receive compressedrefrigerant discharged from the screw compressor, and then separate alubricant from compressed gaseous refrigerant.

In an embodiment, the HVACR system can further include apressure-reducing device. The pressure-reducing device can receivelubricant separated by the lubricant separator and then reduce pressureof the lubricant so that at least a portion of the refrigerant in thelubricant evaporates. The pressure-reducing device then directs thelubricant to the internal heat exchanger for improving a viscosity ofthe lubricant. In an embodiment, the pressure-reducing device isdisposed within the compressor. In an embodiment, the pressure-reducingdevice is separate (e.g., physically separate) from the compressor. Inan embodiment, the pressure-reducing device can be an expansion deviceof the HVACR system.

In an embodiment, a method for improving viscosity of lubricant to acompressor includes reducing a pressure of a lubricant containingrefrigerant by a pressure-reducing device; and heating the lubricantcontaining refrigerant in an internal heat exchanger of the compressor.

The compressor can be, but is not limited to, a screw, scroll,reciprocating, or centrifugal compressor.

In an embodiment, the compressor can include male and female rotors thatcan be supported by bearings such as, for example, radial and axialbearings at a discharge end of the compressor. The rotors can beenclosed within a rotor and motor housing, and the bearings can beenclosed and/or supported by a bearing housing assembly. The bearinghousing assembly can include a bearing housing and bearing cover. Thebearing housing assembly can be, for example, positioned at the axialend of the rotor housing. The bearing cover can be attached to thebearing housing to form an enclosed space.

During operation, the male and female rotors of the compressor canrotate in opposite direction and mesh with each other. The meshingrotors draw refrigerant vapor and force the refrigerant vapor movingalong the rotors. As the refrigerant vapor progresses, the refrigerantvapor is compressed with higher temperature as the volume space betweenthe rotors decreases. The compressed refrigerant vapor can be dischargedout of the compressor with high heat and pressure through a dischargeport.

In an embodiment, the compressor can include intermeshing scrolls, abearing, a motor, and housings. The intermeshing scrolls can include anorbiting scroll member and a fixed scroll member. An orbiting motion ofthe orbiting scroll member relative to the fixed scroll member createspockets that trap refrigerant gas. The pocket becomes increasinglysmaller as the refrigerant gas moves toward a center of the fixed scrollmember, and thereby the refrigerant gas is compressed and pressurized,accompanied by an increasing temperature. The compressed refrigerantreaches the highest pressure and temperature at the center of the fixediron scroll member and then is discharged through a discharge port.

In an embodiment, the compressor can include a muffler.

The compressor can be used to compress working fluids, such as forexample refrigerant vapor.

The compressor can be provided with lubricant, which is used tolubricate, seal, and protect running surfaces of a component, forexample bearings, within the compressor. During operation of thecompressor, some lubricant in the compressor is mixed with refrigerantsuch that the lubricant leaving the compressor contains an amount ofrefrigerant. This may cause, for example, inadequate supply of lubricantto the compressor. In an HVACR system, the lubricant discharged from thecompressor can be circulated back into the compressor such as cavitiesof the bearings to maintain an adequate supply of the lubricant.

In an embodiment, a lubricant separator can be provided upstream ordownstream of the compressor to separate the lubricant from therefrigerant discharged from the compressor. However, the lubricantseparated from the lubricant separator can contain an appreciable amountof refrigerant, as the refrigerant may dissolve in the lubricant. Thismay lower purity of the lubricant and in turn reduce, for example,viscosity of the lubricant. Low viscosity can cause insufficientlubrication, sealing, and/or protection of the running surfaces withinthe compressor.

Generally, a desirable viscosity range for a lubricant may vary withregard to the type of compressor and/or operation of the compressor. Alubricant used in a compressor in an HVACR system may have a peakviscosity at a temperature higher than a saturation temperature of therefrigerant.

Removing refrigerant dissolved in the lubricant can improve theviscosity of the lubricant to be recycled back into the compressor. Thiscan be achieved by reducing pressure of the lubricant and heating thelubricant.

By reducing the pressure of the lubricant, a portion of the refrigerantcontained in the lubricant can evaporate due to the loss of pressure.The evaporation of the refrigerant may lower the temperature of thelubricant.

By adding heat to the lubricant whose pressure and temperature have beenreduced, another portion of refrigerant can be boiled from thelubricant. Thereby, the viscosity of the lubricant can be furtherimproved. Generally, if the pressure and temperature of a lubricantcontaining refrigerant is lowered, for example, by a pressure reducer,and subsequently heat is added to the lubricant, refrigerant can beremoved from the lubricant-refrigerant mixture.

By combining the processes of reducing the pressure of a lubricant andadding heat to the lubricant, the viscosity of the lubricant can beimproved to a desirable level.

The process of reducing pressure can be performed by any suitablepressure-reducing device known in the art that has a mechanism forreducing pressure. The pressure-reducing device can including but notlimited to an expander, pressure reducer, pressure regulator, orifice,expansion valve, or the like. In an embodiment, the pressure-reducingdevice can be a dedicated device. In an embodiment, thepressure-reducing device can be an expansion device of a refrigerantcircuit of an HVACR system.

The process of adding heat to the lubricant can be implemented bycreating an internal heat exchanger within a compressor so that thesystem heat can be utilized to boil off refrigerant from the lubricant.

The term “boil off,” as used in this Specification, means thatrefrigerant contained in a lubricant is driven out of the lubricant byheat.

The term “system heat,” as used in this Specification, means heatgenerated by the compressor due to compressing a working fluid such as,for example, refrigerant. In an embodiment, system heat can include heatfrom a motor driving the compressor.

The internal heat exchanger can include a single or a plurality ofpassages. The passage(s), in part or as a whole, can be provided orformed on a surface or within a body of a component of the compressor.The component can be used to transfer system heat to boil offrefrigerant from the lubricant returning to the compressor.

In an embodiment, the passage(s), in part or as a whole, can extendwithin a body of a component of the compressor. In an embodiment, thepassage(s), in part or as a whole, can be integrated into a body, forexample a wall, of a component of the compressor.

In an embodiment, the passage(s), in part or as a whole, can be extendedonto a surface of a component of the compressor. In an embodiment, theinternal heat exchanger, in part or as a whole, can be integrated ontoor into a surface of a component of the compressor. The surface caninclude an interface surface or non-interface surface. The interfacesurface in an embodiment can be a machined surface between mating partssuch as bearing housing to rotor housing. A non-interface surface in anembodiment can have a cover and bolts. In an embodiment, the surface canbe a face of the component. The “face” means any flat surface of acomponent of the compressor.

The component of the compressor can be any part of the compressor thatcan accommodate the passage(s) of the internal heat exchanger and cantransfer sufficient system heat. In an embodiment, the component can bea part exposed to discharge temperature. In an embodiment, the componentcan be a part whose temperature is greater than a suction temperature ofthe compressor. In an embodiment, the component can be a part near orclose to the discharge port of compressor. In an embodiment, thecomponent of the compressor can include but not limited to a bearinghousing cover, bearing housing, rotor housing, motor housing, and/ormuffler.

In an embodiment, the passage(s) of the internal heat exchanger, in partor as a whole, can be provided within a casting of a bearing housingcover, bearing housing, rotor housing, motor housing, or muffler of thecompressor. The casting of the bearing housing, rotor housing, motorhousing, or muffler of the compressor can accommodate the passage(s) andtransfer system heat. In an embodiment, the passage(s), in part or as awhole, extend within a bottom of the casting of the bearing housing,rotor housing, or motor housing.

In an embodiment, the passage(s), in part or as a whole, can be providedonto a surface of a bearing cover, bearing housing, rotor housing, motorhousing, or a muffler of the compressor. In an embodiment, thepassage(s), in part or as a whole, can extend on an interface of thecasting of a bearing housing, rotor housing, motor housing, or mufflerof the compressor. In an embodiment, the passage(s), in part or as awhole, can be provided on a face of the casting of the bearing housingcover, bearing housing, rotor housing, motor housing, or muffler of thecompressor.

The passage(s), in part or as a whole, can be machined passages(s).

The passage(s), in part or as a whole, can be formed by any suitablemeans including but not limited to casting, etching, drilling, milling,retrofitting, welding, or a combination thereof.

In an embodiment, the passage(s), in part or as a whole, can, but notlimited to, be casted within the bearing housing, rotor housing, motorhousing, or muffler of the compressor. In an embodiment, the passage(s),in part or as a whole, is drilled hole(s) within the casting of thebearing housing, bearing cover, rotor housing, motor housing, or mufflerof the compressor. In an embodiment, the passage(s), in part or as awhole, can be milled on a surface of the bearing housing cover, bearinghousing, rotor housing, motor housing, or muffler of the compressor.

The bearing housing can be disposed at or near the discharge end wherethe compressed hot refrigerant is discharged. In some circumstances, forexample, the temperature of the casting of the bearing housing may behigher than those of the rotor housing and the motor housing.

The passage(s) of the internal heat exchanger can be configured to anytype of flow arrangements. In an embodiment, the internal heat exchangercan be configured to include a single-pass or multi-pass passage. In anembodiment, the internal heat exchanger can be configured to includemultiple parallel single-pass passages.

The passage(s), in part or as a whole, can adopt any suitableconfiguration, such as geometry and shape, that can transfer sufficientsystem heat to the lubricant flowing therein. The configuration caninclude but not limited to serpentine, straight, and/or curvedconfigurations. In an embodiment, the passage(s) can be configured toform one or more serpentine single-pass passages. In an embodiment, thepassage(s) can be configured to form one or more serpentine multi-passpassages, so that the lubricant can flow back and forth for multipletimes to increase the heat transfer efficiency.

The compressor can be a component of a system. In an embodiment, thesystem can be an HVACR system. The HVACR system can include a lubricantsource and a pressure-reducing device, in addition to a compressorcontaining the internal heat exchanger. In an embodiment, the lubricantsource can be a lubricant separator. The lubricant separator can receivecompressed refrigerant discharged from the compressor, and then separatelubricant from gaseous compressed refrigerant. The pressure-reducingdevice can reduce pressure of the lubricant received from the lubricantseparator so that at least a portion of the refrigerant in the lubricantevaporates due to loss of pressure. The lubricant can be routed to theinternal heat exchanger for further improvement of viscosity. Thus, thelubricant separator, pressure-reducing device, and internal heatexchanger can constitute a pathway for refining the lubricant to becycled back to the compressor.

The lubricant separator can be disposed upstream or downstream of thecompressor. In an embodiment, the lubricant separator is fluidlydisposed between the compressor and the condenser. In an embodiment, thelubricant separator is disposed upstream of the compressor.

The lubricant separator can be any suitable device known in the art thathas a mechanism for separating lubricant from refrigerant. In anembodiment, the lubricant separator can be an oil tank or reservoir. Thelubricant separator can be a dedicated or non-dedicated device. In anembodiment, an oil reservoir is deposed upstream of the compressor forseparating lubricant from refrigerant. In an embodiment, an evaporatorof a refrigerant circuit of an HVACR system can function as anon-dedicated lubricant separator.

The pressure-reducing device can be disposed within the compressor oroutside of the compressor. In an embodiment, the pressure-reducingdevice is disposed within the compressor. In an embodiment, thepressure-reducing device is disposed outside of the compressor.

The pressure-reducing device can include, but is not limited to, apressure regulator or expansion device. In an embodiment, thepressure-reducing device is an orifice. In an embodiment, thepressure-reducing device can be an expander such as, for example, anexpansion valve. In an embodiment, the pressure-reducing device can bean expansion device of the refrigerant circuit of the HVACR system.

A method, which uses the internal heat exchanger, the compressor, or thesystem for improving the viscosity of a lubricant to be cycled back intothe compressor, can include reducing a pressure of a lubricantcontaining refrigerant by a pressure-reducing device and heating thelubricant containing refrigerant in the internal heat exchanger of thecompressor with system heat to obtain a refined lubricant.

In an embodiment, the method can further include directing arefrigerant-lubricant mixture discharged from the compressor to alubricant separator.

In an embodiment, the method can further include directing a lubricantcontaining refrigerant from the lubricant separator to apressure-reducing device.

In an embodiment, the method can further include directing a lubricantcontaining refrigerant from the pressure-reducing device to the internalheat exchanger of the compressor.

In an embodiment, the method can further include directing a lubricantfrom the internal heat exchanger to cavities of bearings of thecompressor.

The internal heat exchanger, system, and method herein can improveviscosity of the lubricant returning to a compressor to a desirablelevel without use of a sump. A sump is a device that can receive boththe lubricant separated from the lubricant separator and a hot lubricantdirectly from the compressor, for example the bearings. The hotlubricant heats the lubricant separated from the lubricant separator inthe sump, and as such a portion of refrigerant in the lubricant can beboiled off. However, the sump can increase the complexity and cost ofthe system.

FIG. 20 illustrates a schematic view of a refrigeration system 6001,with which the embodiments as disclosed herein can be practiced. Therefrigeration system 6001 provides benefits for improving viscosity ofthe lubricant returning to a compressor by utilizing system heatgenerated in the compressor. The lubricant may be cycled to, forexample, lubricate, seal, and cool moving surfaces within the compressor6100.

Referring to FIG. 20, the refrigeration system 6001 can include acompressor 6100, a lubricant separator 6200, a condenser 6300, anexpansion device 6400, and an evaporator 6500. In an embodiment, thelubricant separator 6200 may not be present or can be included at adifferent location of the refrigeration system 6001. The compressor 6100can include bearings 6102, rotors 6104, an internal heat exchanger 6106,and a pressure-reducing device 6108. The internal heat exchanger 6106 isdisposed within the compressor 6100. The internal heat exchanger 6106 isin fluid communication with cavities of the bearings 6102 and with thepressure-reducing device 6108. The pressure-reducing device 6108 isfurther in fluid communication with the lubricant separator 6200. Thelubricant separator 6200 is further in fluid communication with thecompressor 6100 and the condenser 6300. The lubricant separator 6200,the pressure-reducing device 6108, and the internal heat exchanger 6106can constitute a return pathway to circulate the lubricant back to thecompressor 6100.

In operation, the compressor 6100 compresses gaseous refrigerant. Thecompressed gaseous refrigerant is discharged together with lubricant asa high-pressure refrigerant-lubricant mixture. The compressor 6100 thendelivers the high-pressure superheated refrigerant-lubricant mixturethrough a line 6010 to the lubricant separator 6200. The lubricantseparator 6200 separates the lubricant from the compressed gaseousrefrigerant at high pressure. In an embodiment, the lubricant separator6200 can include an oil reservoir. The lubricant, even after separation,may contain an appreciable amount of refrigerant, which can lowerviscosity of the lubricant. As a result, the lubricant may not havesufficient viscosity to lubricate the running surfaces of the compressor6100 including the bearings 6102.

If the lubricant from the lubricant separator 6200 at high pressure isdirectly circulated into the bearings 6102 at low pressure, a proportionof the refrigerant may evaporate from the lubricant. However, this wouldnot increase viscosity of the lubricant to a sufficient level.

In the embodiment illustrated by FIG. 20, the viscosity of the lubricantreturning the compressor 6100 can be improved by both reducing pressureand increasing temperature of the lubricant.

The lubricant from the lubricant separator 6200 enters thepressure-reducing device 6108 through passage 6016. Thepressure-reducing device 6108 lowers the pressure of the lubricant, anda proportion of refrigerant in the lubricant evaporates due to loss ofpressure. The evaporation of refrigerant also reduces temperature of thelubricant. In an embodiment, the pressure-reducing device 6108 is anorifice. In an embodiment, the pressure-reducing device 6108 can be anexpansion valve. In an embodiment, the pressure-reducing device 6108 canbe expander.

After pressure reduction, the lubricant from the pressure-reducingdevice 6108 enters the internal heat exchanger 6106 through line 6020.The internal heat exchanger 106 can utilize system heat generated in thecompressor 6100 to increase temperature of the lubricant, so that anadditional proportion of refrigerant can be driven out of the lubricantto further improve viscosity. In an embodiment, the internal heatexchanger 6106 absorbs the system heat in the compressor 6100 to boiloff refrigerant contained in the lubricant. In an embodiment, thepressure-reducing device 6108 is configured to reduce the pressure ofthe lubricant as much as possible.

The internal heat exchanger 6106 can be integrated with a componentwithin the compressor 6100. The internal heat exchanger 6106 can includepassage(s) where the lubricant flows. The passage(s) of the internalheat exchanger 6106, in part or as a whole, can be integrated forexample within or on a surface of the bearing housing assembly, rotorhousing, motor housing, or muffler of the compressor 6100.

The passage(s) of the internal heat exchanger 6106, in part or as awhole, can be machined passage(s). In an embodiment, the passage(s), inpart or as a whole, can be drilled in a bottom of the bearing housing,rotor housing, or motor housing of the compressor 6100. In anembodiment, the passage(s), in part or as a whole, can be casted in abottom of the bearing housing, rotor housing, or motor housing of thecompressor 6100.

In an embodiment, the passage(s) of the internal heat exchanger 6106 canbe milled on a surface, for example an interface surface, within thecompressor 6100. In an embodiment, the passage(s) can be milled on aninterface surface of the bearing housing, rotor housing, motor housing,or muffler of the compressor 6100.

In an embodiment, the flow rates of the lubricant in the heat exchanger6106 and/or the pressure-reducing device 6108 can be controlled tooptimize heat transfer to the lubricant and/or pressure reduction of thelubricant, achieving an excellent performance in degassing and raisingtemperature. In an embodiment, the flow rates can be controlled by usinga solenoid valve or other regulating valve or flow control method. In anembodiment, the flow rates could be controlled by logic defined bycompressor operating parameters to optimize the flow and heat transfer.

The lubricant can be optionally further heated by mixing with a hotlubricant from the compressor 6100 such as the bearing 6102 and therotor 6104. In an embodiment, the hot lubricant from the compressor 6100flows through line 6021 and enters into passage 6022 to further vaporizethe refrigerant in the lubricant, before the lubricant returns to thecompressor 6100.

The fluid entering cavities of the bearings 6102 includes gaseousrefrigerant and a refined lubricant. The refined lubricant is a liquid.The fluid to enter the cavities of the bearings 6102 is a two-phasefluid. Both the refined lubricant and the gaseous refrigerant can enterinto the cavities of the bearings 6102. In an embodiment, the gaseousrefrigerant is separated from the refined lubricant by, for example, aninternal lubricant separator, so that the refined lubricant enters intothe cavities of the bearings 6102. The gaseous refrigerant separatedfrom the refined lubricant merges with refrigerant from the evaporator6500 through line 6024. In an embodiment, the line 6024 is provided witha flow regulator 6023 to direct flow of the gaseous refrigerantseparated from the refined lubricant.

The compressed high-pressure gaseous refrigerant separated from thelubricant separator 6200 enters the condenser 6300 through passage 6014.In the condenser 6300, the compressed high-pressure gaseous refrigerantis cooled and condenses into a liquid phase. The refrigerant then passesan expansion device 6400 and enters the evaporator 6500 through lines6018 and 6019. The liquid refrigerant in the evaporator 6500 evaporatesinto a gaseous phase. The gaseous refrigerant then enters the compressor6100 through passage 6026.

FIG. 21 illustrates another schematic view of a refrigeration system6002, with which the embodiments as disclosed herein can be practiced.

Referring to FIG. 21, the compressor 6100 compresses a gaseousrefrigerant. The compressed gaseous refrigerant is discharged from thecompressor 6100 together with an appreciable amount of lubricant,forming a compressed high-pressure refrigerant-lubricant mixture. Thecompressor 6100 then delivers the compressed high-pressurerefrigerant-lubricant mixture through a line 6010 to the condenser 6300.The compressed high-pressure refrigerant-lubricant mixture gets cooledin the condenser 6300, and gaseous refrigerant in this mixture istransformed into liquid refrigerant. The condenser 6300 then deliversthe refrigerant-lubricant mixture to an expansion device 6400 and theevaporator 6500 through lines 6018 and 6019. The expansion device 6400reduces the pressure of the refrigerant-lubricant mixture, so that theliquid refrigerant evaporates into a gaseous phase in evaporator 6500,which cools the air flowing through the evaporator 6500. In anembodiment, the lubricant, which is in liquid form, and some residualliquid refrigerant settle down in the evaporator 6500, forming alubricant-refrigerant mixture. In an embodiment, the expansion device6400 reduces the pressure of the lubricant discharged from thecompressor 6100. This lubricant-refrigerant mixture is then delivered toan optional pressure-reducing device 6108 through line 6016 to furtherlower the pressure of the lubricant-refrigerant mixture. As such, anadditional proportion of the refrigerant may flash out of thelubricant-refrigerant mixture due to reduction of the pressure, whichmay also further reduce the temperature of the lubricant-refrigerant. Inan embodiment, a pump type device is provided at, for example, the line6016 to drive the lubricant-refrigerant mixture toward the internal heatexchanger 6106. The pump type device can be any types of pumper know inthe art that has a mechanism for pumping the lubricant-refrigerantmixture. The lubricant-refrigerant mixture is then delivered to theinternal heat exchanger 6106 through passage 6020. The heat exchanger6106 further boils off refrigerant from the lubricant-refrigerantmixture to obtain a refined lubricant with sufficient viscosity forlubricating and sealing running surfaces within the compressor 6100.

The refined lubricant can be optionally further heated by mixing withhot lubricant from the compressor 6100 such as the bearing 6102 and therotor 6104. In an embodiment, the hot lubricant from the compressor 6100flows through line 6021 and enters into passage 6022 to further boil offthe refrigerant from the refined lubricant, before the refined lubricantreturns to cavities of the bearings 6102 though the passage 6022.

Both the gaseous refrigerant and the refined lubricant can enter intocavities of the bearings 6102 through passage 6022.

In an embodiment, the gaseous refrigerant is separated from the refinedlubricant, so that the refined lubricant enters into the bearings of6102. In an embodiment, the separated gaseous refrigerant merges withthe gaseous refrigerant from the evaporator 6500 through line 6024 andthen enters the compressor 6100 through line 6026 for compression. In anembodiment, the line 6024 is provided with a flow regulator 6023directing the flow of the gaseous refrigerant separated from the refinedlubricant.

FIG. 22 illustrates an example of the compressor 6100, with which theembodiments as disclosed herein can be practiced.

Referring to FIG. 22, the compressor 6100 is a screw compressor andfurther includes a bearing assembly 6130, a rotor housing 6140, and amotor housing 6150.

The bearing assembly 6130 includes a bearing housing 6132 and a bearingcover 6134. The bearing assembly 6130 houses bearings. The compressedworking fluid such as refrigerant can be discharged through the bearingassembly 6130. The bearing assembly 6130 covers the rotor housing 6140at the axial end.

The rotor housing 6140 houses rotors 6142 a and 6142 b. The rotorhousing may have a suction port 6176 and discharge port 6178. Thesuction port 6176 and discharge port 6178 are in fluid communicationwith the working chamber 6144. The suction port 6176 and the dischargeport 6178 may each be an axial port, a radial port, or a combination ofa radial and an axial port.

The suction port 6176 may receive the refrigerant at a suction pressureand a suction temperature. The compressor 6100 compresses therefrigerant as the compressor 6100 communicates the refrigerant from thesuction port 6176 to the discharge port 6178.

In an embodiment, the motor housing 6150 houses an electric motor 6152.The electric motor 6152 drives meshed screw rotors 6142 a, 6142 b. In anembodiment, the motor housing 6150 may be integral to the rotor housing6140.

FIG. 23 illustrates an embodiment of the internal heat exchanger 6106including passages drilled or casted within the bottom wall of thecasting of the bearing housing 6132 of a compressor, according to anembodiment.

Referring to FIG. 23, the embodiment of the internal heat exchanger 6106can include a plurality passages. In an embodiment, the internal heatexchanger includes seven internal passages provided within the bottomwall of the casting of the bearing housing 6132 of a compressor. Theseven internal passages are 6410, 6412, 6414, 6416, 6418, 6420, and6422. The seven internal passages can be arranged in a parallel manner.It is understood that the number and the arrangement of the internalpassages in the embodiment of the internal heat exchanger 6106 isexemplary and can be other number and/or arrangement that can transfersufficient system heat for boiling off refrigerant out of lubricant.

The seven passages can be configured to a serpentine seven-pass passageby other passages including passages 6413, 6417, and 6421, with thepassage 6410 being an inlet and the passage 6422 being an outlet in anembodiment. The serpentine seven-pass passage allows the lubricant toflow back and forth seven times to absorb system heat to remove therefrigerant contained in the lubricant. As such, the lubricant canbecome refined with sufficient viscosity to lubricating and sealing therunning surfaces within the compressor. It is understood that the seveninternal passages can be configured to any other flow configurationwithout being limited particular to the serpentine seven-pass passages.In an embodiment, the seven internal passages 6410, 6412, 6414, 6416,6418, 6420, and 6422 can be configured to form multiple parallelsingle-pass passages.

The passage 6422 is in fluid communication with passage 6430. Thepassage 6430 is further in fluid communication with passage 6435 that isin fluid communication with cavities of the bearings of the compressor.The passage 6435 can receive a fluid from the passage 6422 and route thefluid to the cavities of the bearings 6102 of the compressor.

A length of each passage is not particularly limited but can bedependent on a flow rate and temperature rise needed. In an embodiment,each of the passages 6410, 6412, 6414, 6416, 6418, 6420, and 6422 canhave a length of at or about 6020 inches. Thus, the total length of theserpentine seven-pass passage is at or about 6140 inches. It isunderstood that any other suitable length of passages can be chosen totransfer sufficient heat to boil off refrigerant out of the lubricant.

In an embodiment, the passages can be formed by for example machining.The passages can be manufactured by any suitable means including but notlimited to drilling, casting, etching, retrofitting, etc.

The bottom wall of the bearing housing 6132 can have a sufficientthickness for accommodating the passages. In an embodiment, thepassages, in part or as a whole can be manufactured by casting holeswithin the bottom wall of the bearing housing 6132 of the compressor. Inan embodiment, the passages, in part or as a whole, can be manufacturedby milling and/or retrofitting in addition to casting and/or drilling.It is understood that the above embodiment illustrated by FIG. 23 ismerely an example. The passages can be machined in any suitable locationof the bearing housing, rotor housing, or motor housing of thecompressor, depending on their shape, size, and design, if the locationcan accommodate the passages and can provide sufficient system heat toboil off the refrigerant out of the lubricant.

FIG. 24 illustrate an embodiment of the internal heat exchanger 6106including surface passages 6510 and 6520 provided on a surface of abearing housing of a compressor according to an embodiment.

Referring to FIG. 24, the embodiment of the internal heat exchanger 6106includes passages 6510 and 6520 provided on a surface of the bearinghousing assembly of a compressor. In an embodiment, the passages 6510and 6520 are milled on a surface of the bearing housing of thecompressor. In an embodiment, the passages 6510 and 6520 are provided onan interface surface of the bearing housing of the compressor. In anembodiment, the interface can be an interface surface between thebearing housing and the rotor housing. It is understood that theembodiment of the internal heat exchange 6106 can include one (1) ormore than two (2) passages.

The two passages 6510 and 6520 are fluidly connected with thepressure-reducing device 6108. In an embodiment, the two passages 6510and 6520 can further respectively fluidly connected with passages 6530and 6540 below the interface surface of the bearing housing of thecompressor. In an embodiment, the passages 6530 and 6540 can be furtherin fluid communication with cavities of the bearings of the compressor.

The passages 6510 and 6520 can have a serpentine shape. The embodimentof the internal heat exchanger 6106 absorbs the system heat of thecompressor to boil off liquid refrigerant in the lubricant. As such, thelubricant becomes refined with excellent viscosity before entering intobearings 6102 of the compressor.

It is understood that the embodiment illustrated by FIG. 24 is anexample. In an embodiment, the passages 6510 and 6520 can be provided ona surface of the rotor housing, muffler, or motor housing of thecompressor.

The passages 6510 and 6520 are milled on a surface of the bearinghousing assembly. It is understood that the passages 6510 and 6520 canalso be manufactured by any other suitable means such as for exampleetching, welding, and the like. In an embodiment, the passages 6530 and6540 are drilled within the bearing housing assembly. It is understoodthat the passages 6530 and 6540 can also be manufactured by any othersuitable means such as for example casting.

Aspects:

Any of aspects 1-6 can be combined with any of aspects 7-9, and any ofaspects 1-9 can be combined with aspect 10. It is understood that any ofaspects 1-10 can be combined with any other aspects recited herein.

Aspect 1. A compressor comprising an internal heat exchanger, whereinthe internal heat exchanger is fluid communication with bearings of thecompressor.

Aspect 2. The compressor of aspect 1, wherein the internal heatexchanger is fluidly connected with a pressure-reducing device.

Aspect 3. The compressor of aspects 1-2, wherein the internal heatexchanger includes passages extended within bearing housing, rotorhousing, motor housing, or muffler of the compressor.

Aspect 4. The compressor of aspects 1-3, wherein the internal heatexchanger includes passage(s) provided onto a surface or interfacesurface of bearing housing, motor housing, motor housing, or muffler ofthe compressor.

Aspect 5. The compressor of aspects 1-4, wherein the internal heatexchanger includes passage(s) casted or drilled within bearing housing,motor housing, motor housing, or muffler of the compressor.

Aspect 6. The compressor of aspects 1-4, wherein the internal heatexchanger includes passage(s) milled on a surface or interface surfaceof bearing housing assembly, motor housing, motor housing, or muffler ofthe compressor.

Aspect 7. A heating, ventilation, air conditioning, and refrigeration(HVACR) system, comprising the compressor of aspects 1-6.

Aspect 8. The HVACR system of aspect 7, wherein the HVACR system furthercomprises a lubricant separator, the lubricant separator receives fluiddischarged from the compressor and separates lubricant from the fluid.

Aspect 9. The HVACR system of aspect 8, wherein the lubricant separatoris in fluid communication with a pressure-reducing device, and thepressure-reducing device is in fluid communication with the internalheat exchanger.

Aspect 10. A method form improving viscosity of lubricant returning tothe compressor of aspects 1-9 for reuse, comprising: reducing a pressureand temperature of a lubricant-refrigerant mixture by apressure-reducing device; and heating the lubricant-refrigerant mixturein an internal heat exchanger of the compressor, wherein thepressure-reducing device evaporates a portion of refrigerant out of thelubricant-refrigerant mixture, the internal heat exchanger absorbssystem heat in the compressor to boil off another portion of refrigerantout of the lubricant-refrigerant mixture.

Disclosure relates to an internal heat exchanger within a compressor, asystem, and a method for improving viscosity of the lubricant to becycled back into the compressor. The internal heat exchanger is in fluidcommunication with a pressure-reducing device, which receives alubricant separated from a refrigerant-lubricant mixture discharged fromthe compressor. The pressure-reducing device lowers pressure of thelubricant, causing a proportion of refrigerant in the lubricantevaporates concurrently with a temperature drop. The lubricant thenflows through the internal heat exchanger, so that another proportion ofrefrigerant in the lubricant can be boiled off to obtain a refinedlubricant. The refined lubricant then enters into cavities of bearingsof the compressor for reuse.

Suction-Line Heat Exchanger (FIGS. 25-27)

This disclosure is related to a refrigeration circuit including asuction line heat exchanger to increase a discharge superheat of thecompressor.

A suction line heat exchanger can allow relatively hot liquid leaving acondenser of a refrigeration circuit to exchange heat with relativelycool gas leaving an evaporator of a refrigeration circuit. This heatexchange can increase the temperature of working fluid that is beingreceived at a suction port of a compressor of the refrigeration circuit.The increased suction temperature in turn can result in increaseddischarge superheat for the discharge of the compressor. Increaseddischarge superheat can improve oil separation and recovery and reduceproblems associated with lubricant being dissolved in the refrigerant,particularly for compressor designs having improved efficiency and forlow global warming potential (low-GWP) refrigerants such as R1234ze.

In an embodiment, a refrigeration circuit includes a compressor, acondenser, an expander, an evaporator, and a suction line heatexchanger. The suction line heat exchanger is configured to exchangeheat between a liquid side receiving a working fluid as a liquid leavingthe condenser, prior to the expander and a gas side receiving theworking fluid as a gas leaving the evaporator, prior to the compressor.The liquid side includes a shell and the gas side includes a pluralityof tubes extending through the shell. The suction line heat exchanger isconfigured such that a discharge of the compressor has a dischargesuperheat of at or about 3.3° C. or more than 3.3° C.

In an embodiment, the refrigerant circuit further includes a throttlingvalve between the plurality of tubes of the suction line heat exchangerand the compressor.

In an embodiment, the shell has a length of at or about one meter andthe shell has a diameter of between at or about 200 millimeters (mm) andat or about 220 mm. The plurality of tubes includes between at or about55 and at or about 65 tubes, and each of the plurality of tubes has aninterior diameter of between at or about 15 mm and at or about 18 mm.

In an embodiment, a pressure drop across the gas side of the suctionline heat exchanger is at or about 10 kPa or less than 10 kPa forrefrigerant R1234ze.

In an embodiment, a temperature of gas leaving the gas side of thesuction line heat exchanger is greater than at or about 1.5° C. greaterthan a temperature of the gas entering the gas side of the suction lineheat exchanger.

In an embodiment, the refrigeration circuit further includes a pluralityof baffles within the shell. Each of the baffles includes a continuousperimeter in contact with an entire inner diameter of the shell and anopen area. In an embodiment, the open area includes at or about 30% ofthe area defined by the continuous perimeter.

In an embodiment, the shell includes a plurality of longitudinal baffleseach extending a length of the shell and extending from an inner surfaceof the shell to one of the plurality of tubes.

In an embodiment, a suction line heat exchanger embodiment includes aliquid side including an inlet connected to a condenser of arefrigeration circuit, an outlet connected to an expander of therefrigeration circuit, and a shell defining an internal space. Thesuction line heat exchanger also includes a gas side including, an inletconnected to an evaporator of the refrigeration circuit, an inlet headerconnecting the inlet to a plurality of tubes, the plurality of tubesextending through the internal space from one end of the shell to anopposing end of the shell, and an outlet header connecting the pluralityof tubes to an outlet. The suction line heat exchanger is configured toincrease a discharge superheat of a compressor of the refrigerationcircuit such that the discharge superheat is at or about 3.3° C. or morethan 3.3° C.

In an embodiment, the shell has a length of at or about one meter andthe shell has a diameter of between at or about 200 millimeters (mm) andat or about 220 mm. The plurality of tubes includes between at or about55 and at or about 65 tubes, and each of the plurality of tubes has aninterior diameter of between at or about 15 mm and at or about 18 mm.

In an embodiment, a pressure drop across the gas side of the suctionline heat exchanger is at or about 10 kPa or less than 10 kPa forrefrigerant R1234ze.

In an embodiment, there is a chamfer where each of the tubes isconnected to the inlet header, and a chamfer where each of the tubes isconnected to the outlet header.

In an embodiment, the suction line heat exchanger further includes aplurality of baffles within the shell. Each of the baffles includes acontinuous perimeter in contact with an entire inner diameter of theshell and an open area. In an embodiment, the open area includes at orabout 30% of the area defined by the continuous perimeter.

In an embodiment, the shell includes a plurality of longitudinal baffleseach extending a length of the shell and extending from an inner surfaceof the shell to one of the plurality of tubes.

In an embodiment, a method of increasing superheat of a refrigerantincludes directing relatively hot liquid refrigerant from a condenser toa suction line heat exchanger; directing relatively cool gaseousrefrigerant from an evaporator to the suction line heat exchanger;performing heat exchange between the relatively hot liquid refrigerantand the relatively cool gaseous refrigerant using the suction line heatexchanger, to increase the heat of the relatively cool gaseousrefrigerant to obtain a heated gaseous refrigerant; and directing theheated gaseous refrigerant to a suction port of the compressor, whereinthe compressor heats and pressurizes the heated gaseous refrigerant toobtain a superheated gaseous refrigerant.

Improvements to efficiency of compressors may reduce superheating by thecompressor. In turn, this can result in difficulty in oil separation andincreased issues with oil saturation in a working fluid. A heatexchanger at the suction line heating working fluid prior to its entryinto the compressor can result in the discharge of the compressor beingsuperheated, improving oil separation. Further, this can increase theavailable portions of the operational map by ensuring sufficientperformance and lubricant separation even at lower capacities.

FIG. 25 illustrates a circuit including a suction-line heat exchangeraccording to an embodiment. The refrigeration circuit 2500 shown in FIG.25 includes a compressor 2502, a condenser 2504, a suction line heatexchanger 2506, expansion device 2508, evaporator 2510, and optionalthrottling valve 2512.

Compressor 2502 is a compressor connected to the refrigeration circuit2500. The compressor 2502 may be, for example, a screw compressor, wherecompression chambers are formed and a fluid such as a working fluid iscompressed by the rotation of two rotors and the engagement of lobes oneach of the rotors. Compressor 2502 may include one or more lubricatedbearings that may, for example, support and allow the rotation ofcomponents of the compressor such as the rotors of a screw compressor.Compressor 2502 can be, for example, any of the compressor embodimentsdescribed herein. Compressor 2502 has an operational map defining itsrange of operation over saturated suction temperatures and saturateddischarge temperatures for the compressor. Compressor 2502 can have aminimum required suction pressure for operation. The discharge ofcompressor 2502 can have a discharge superheat of at least 3.3° C. or ator about 3.3° C. across the entire operating map within which compressor2502 is operated during operation of refrigeration circuit 2500. In anembodiment, the discharge superheat of the compressor 2502 is in therange from at or about 3.3° C. to at or about 25° C. In an embodiment,the compressor 2502 requires a suction pressure in a range from at orabout 1.35 to at or about 5.13 bars.

Condenser 2504 is located downstream of the compressor 2502. Condenser2504 is a component of the refrigeration circuit where the working fluidcompressed by compressor 2502 rejects heat. Condenser 2504 receives theworking fluid in a heated and compressed state from compressor 2502.Condenser 2504 allows the heated and compressed working fluid to rejectheat.

Suction line heat exchanger 2506 allows the exchange of heat between theworking fluid leaving condenser 2504, and the working fluid leavingevaporator 2510. The working fluid leaving condenser 2504 is at arelatively higher temperature than the working fluid leaving evaporator2510. The exchange of heat in suction line heat exchanger 2506 heats theworking fluid from evaporator 2510 that then passes to compressor 2502.The exchange of heat in suction line heat exchanger 2506 also cools theworking fluid from condenser 2504 that then passes to expansion device2508. Suction line heat exchanger 2506 can include a plurality of tubes,a shell and one or more baffles within the shell, which are detailedbelow and shown in FIGS. 26A, 26B, and 27. The suction line heatexchanger 2506 can be configured to provide subcooling sufficient topreserve the cooling capacity of the refrigeration circuit 2500 withoutexcessive pressure drop of the working fluid across the suction lineheat exchanger 2506. The subcooling and pressure drop values may beparticular to the design of a particular refrigerant circuit 2500. In anembodiment, a temperature of gas leaving the gas side of the suctionline heat exchanger 2506 can be in the range from at or about 0° C. toat or about 20° C. In an embodiment, the heating of gas in suction lineheat exchanger can result in a discharge superheat of the compressorbeing increased by at least 1.5° C. or at or about 1.5° C. In anembodiment, a subcooling in suction line heat exchanger 2506 can be atleast 33 kW or at or about 33 kW.

Expansion device 2508 is a device configured to expand the working fluidpassing through. The expansion causes the working fluid to significantlydecrease in temperature. In an embodiment, the expansion device 2508 maybe an expander such as an expansion valve, expansion plate, expansionvessel, orifice, the like, or other such types of expansion mechanisms.It should be appreciated that the expansion device 2508 may be any typeof expander used in the field for expanding a working fluid causing theworking fluid to decrease in temperature.

Evaporator 2510 provides heat exchange between the working fluid leavingexpansion device 2508 and another fluid. In evaporator 2510, the workingfluid absorbs heat from the other fluid, evaporating the working fluid.Working fluid leaving evaporator 2510 then travels to suction line heatexchanger 2506.

Optionally, throttling valve 2512 can be included between suction lineheat exchanger 2506 and compressor 2502. In an embodiment, throttlingvalve 2512 is not included in the refrigeration circuit 2500, and thesuction line heat exchanger 2506 may be directly connected to thesuction of compressor 2502. Throttling valve 2512 can control the flowof working fluid into the suction port of compressor 2502, for exampleto maintain suitable pressure between the evaporator 2510 and thesuction port of the compressor 2502.

FIG. 26A illustrates a perspective view of a suction-line heat exchanger2600 according to an embodiment. FIG. 26B illustrates a side view of thesuction-line heat exchanger 2600 according to the embodiment shown inFIG. 26A. In FIG. 26A, the shell 2602 is omitted such that internalcomponents of the heat exchanger are visible. In FIG. 26B, the tubes2608 are omitted from the sectional view while shell 2602 is included.

Suction line heat exchanger 2600 includes a shell 2602, which is showncut away to allow the interior of suction line heat exchanger 2600 to bevisible. Shell 2602 has an inlet 2604 and an outlet 2606, and aplurality of tubes 2608 connected to an inlet header 2610 and an outletheader 2612. The inlet header 2610 is connected to an inlet 2614 and theoutlet header 2612 is connected to an outlet 2616. Baffles 2618 can beincluded within shell 2602 and surrounding tubes 2608. Suction line heatexchanger 2600 can further include longitudinal baffles 2620.

The suction line heat exchanger 2600 can be configured to providesubcooling sufficient to preserve the cooling capacity of arefrigeration circuit and without excessive pressure drop of the workingfluid across the suction line heat exchanger 2600. In an embodiment, thesubcooling provided by suction line heat exchanger 2600 can be at least33 kW or at or about 33 kW. For example, the heating of the fluidpassing through tubes 2608 can be sufficient that the dischargesuperheat of a compressor receiving the fluid is at least 3.3° C. or ator about 3.3° C., for example, across the entire operating map of thecompressor. In an embodiment, the suction line heat exchanger 2600 addsat least 1.5° C. or at or about 1.5° C. to the temperature of gaspassing through tubes 2608. In an embodiment, the pressure drop is suchthat the fluid leaving the suction line heat exchanger 2600 has apressure greater than a minimum suction pressure of the compressor. Inan embodiment, a pressure drop for the relatively cool gas across thesuction line heat exchanger 2600 is at or about 10 kPa or less than 10kPa. This configuration can include parameters including the number anddiameter of tubes 2608, the length of the shell 2602, features such as aconical inlet and outlet headers 2610, 2612, chamfering of the inlets toeach of the tubes 2608, and the like.

Shell 2602 receives working fluid from a first point in a refrigerationcircuit, such as refrigeration circuit 2500 described above and shown inFIG. 25. In an embodiment, the working fluid received by and conveyedthrough shell 2602 is a relatively hot liquid received from a condenser,such as condenser 2504 discussed above and shown in FIG. 25. In anembodiment, the length and/or the diameter of shell 2602 is based on,for example, one or more of the available space in an HVACR unit, thedesired heat exchange at the suction line heat exchanger 2600, and thetemperature, density, and/or flow rates of the fluids within shell 2602and tubes 2608, respectively. In an embodiment, shell 2602 is at orabout one meter in length. In an embodiment, shell 2602 is at or about1006 mm in length. In an embodiment, shell 2602 has an exterior diameterof between at or about 200 mm and at or about 220 mm. In an embodiment,shell 2602 has an interior diameter of between at or about 195 mm to 202mm.

Shell 2602 has an inlet 2604 and an outlet 2606. Inlet 2604 is an inletin fluid communication with a hot liquid source such as a condenser of arefrigerant circuit, such as condenser 2504. Outlet 2606 allows fluid toexit shell 2602 once it has exchanged heat with the fluid in the tubes2608. Outlet 2606 may be in fluid communication with an expanderincluded in the refrigeration circuit such as expansion device 2508described above and shown in FIG. 25. In an embodiment, shell 2602,inlet 2604 and outlet 2606 form the liquid side of suction line heatexchanger 2600.

A plurality of tubes 2608 extend through shell 2602. The tubes 2608 aresealed from the interior of shell 2602 such that fluid in tubes 2608cannot mix with fluid within the shell 2602. The number of tubes can beselected based on the values defining a sufficient exchange of heatbetween the fluids, and properties of the fluids including, for example,their temperature, flow rate, density, and the like. The size of shell2602 may be affected by the number and size of tubes 2608. In anembodiment, suction line heat exchanger 2600 includes sixty-one tubes2608. The tubes 2608 may have a length and a diameter selected to allowsufficient heat exchange within the suction line heat exchanger 2600. Inan embodiment, sufficient heat exchange can be defined based on one ormore of the refrigerant used as the working fluid, such as, for example,R1234ze, a lubricant used in a compressor connected to the suction lineheat exchanger 2600, the operating map of the compressor, compressorflow, compressor efficiency, discharge superheat for portions of theoperating map, and the temperatures of the working fluid in therelatively hot liquid state entering shell 2602 and the relatively coolgaseous state entering tubes 2608. The tubes 2608 are made of athermally-conductive material allowing heat transfer between the fluidin shell 2602 and the fluid in each of the tubes 2608. In an embodiment,the tubes are made of copper. In an embodiment, the material of thetubes is selected based on other parameters such as one or more of thelength of the tubes 2608 and/or the shell 2602, the rates of fluid flowthrough the shell 2602 and/or the tubes 2608, the temperatures of thefluid in each of the shell 2602 and tubes 2608, and the like, to allowsufficient heat exchange within the suction line heat exchanger 2600. Inan embodiment, the length of each of the tubes 2608 is the same as thelength of shell 2602. In an embodiment, the length of each of the tubes2608 is at or about approximately one meter. In an embodiment, the outerdiameter of each of the tubes 2608 is from at or about 18 mm to at orabout 19 mm. In an embodiment, the thickness of the wall of each of thetubes 2608 is between at or about 2.3 mm and at or about 2.6 mm. In anembodiment, the interior diameter of each of the tubes 2608 is betweenat or about 15.4 mm and at or about 16.7 mm.

The tubes 2608 are each connected to an inlet header 2610 and also to anoutlet header 2612. The inlet header 2610 is connected to an inlet 2614and the outlet header 2612 is connected to an outlet 2616. In anembodiment, the inlet header 2610 is generally conical and chamfered inshape, having a smaller diameter at the inlet 2614 and a larger diameterat shell 2602. In an embodiment, the outlet header 2616 is generallyconical and chamfered in shape, having a smaller diameter at the outlet2616 and a larger diameter at shell 2606.

In an embodiment, the working fluid received at inlet header 2610 anddivided to flow through the plurality of tubes 2608 is a relatively coolgas received from an evaporator of a refrigeration circuit including thesuction line heat exchanger 2600. The relatively cool gas is at atemperature lower than the temperature of the relatively hot liquidreceived at and passing through shell 2602. In an embodiment, there is achamfer where each of the tubes 2608 meets the inlet header 2610, tofacilitate flow into each of the tubes 2608 and reduce pressure drop.

Outlet header 2612 receives working fluid from tubes 2608 as a gas thathas been heated by heat exchange with the relatively hot liquid in shell2602. Each of tubes 2608 joins outlet header 2612, where the flows fromthe tubes combine and are conveyed to outlet 2616. In an embodiment,where each of the tubes 2608 joins the outlet header 2612, the tubeshave a chamfered surface expanding towards outlet header 2612 tofacilitate flow from tubes 2608 into outlet header 2612 and reducepressure drop.

The outlet 2616 allows the working fluid that entered at inlet 2614 andwas directed through tubes 2608 to leave the suction line heat exchanger2600. In an embodiment, the outlet 2616 is connected to a suction portof a compressor of a refrigeration circuit. At outlet 2616, the workingfluid has a greater temperature than it did at inlet 2614 of the suctionline heat exchanger 2600. The relatively heated working fluid can resultin an increased discharge superheat once the working fluid is compressedby the compressor and discharged, compared to working fluid in anotherwise equivalent refrigeration circuit lacking suction line heatexchanger 2600. In an embodiment, tubes 2608, inlet header 2610, outletheader 2612, inlet 2614, and outlet 2614 form the gas side of suctionline heat exchanger 2600.

Baffles 2618 can be included within shell 2602 and surrounding tubes2608. In an embodiment, two baffles 2618 are located within shell 2602.Baffles 2618 are configured to partially obstruct and/or redirect flowthrough the shell 2602. The direction of flow of fluid through shell2602 by baffles 2618 can improve the exchange of heat between the fluidwithin shell 2602 and the fluid in tubes 2608. In an embodimentincluding multiple baffles, the baffles can each be orienteddifferently, so that areas allowing fluid to pass each of the baffles2618 do not overlap one another or only partially overlap one anotherwhen viewed in the longitudinal direction of shell 2602. At least aportion of baffles 2618 surround a portion of the tubes 2608 of thesuction line heat exchanger 2600, such that fluid cannot pass betweenthose tubes 2608 and the baffle 218. In an embodiment, the baffles 2618are according to the design of baffle 2800 described below and shown inFIG. 27.

Longitudinal baffles 2620 can also be provided within shell 2602.Longitudinal baffles 2620 can extend all or less than all of the lengthof the interior surface of the shell 2602. Longitudinal baffles 2620 andbaffles 2618 can limit or reduce the amount of fluid flow bypassingtubes 2608 at the wall of the shell 2602. In an embodiment, twolongitudinal baffles 2620 are provided. In an embodiment, thelongitudinal baffles are at positions within shell 2602 opposing oneanother. Longitudinal baffles 2620 may pass through baffles 2618 atnotches formed within those baffles. Longitudinal baffles 2620 can eachextend from the inner surface of shell 2602 to an outer surface of oneof the plurality of tubes 2608. In an embodiment, each of thelongitudinal baffles 2620 extends from the inner surface of the shell2602 to the nearest tube of the plurality of tubes 2608. In anembodiment, longitudinal baffles 2620 further assist in aligning andpositioning the other components of suction line heat exchanger 2600.While longitudinal baffles 2620 are shown in a suction line heatexchanger 2600, longitudinal baffles 2620 can be included in anysuitable shell and tube design heat exchanger.

FIG. 27 illustrates a heat exchanger baffle 2700 according to anembodiment. In an embodiment, one or more of the heat exchanger baffle2700 can be included in a suction line heat exchanger such as suctionline heat exchanger 2600 described above and shown in FIGS. 25 and 26.

The heat exchanger baffle 2700 generally includes a continuous perimeter2702 corresponding to the inner shape of the shell of the heatexchanger, such as shell 2602 described above and shown in FIGS. 26A and26B. The heat exchanger baffle 2700 includes a fluid passage 2704, andchannels 2706 corresponding to the size, shape and position of tubesoutside the fluid passage 2702, such as tubes 2608 described above andshown in FIGS. 26A and 26B. The heat exchanger baffle 2700 can furtherinclude notches 2708 configured to accommodate longitudinal baffles suchas longitudinal baffles 2620 described above and shown in FIGS. 26A and26 B.

Continuous perimeter 2702 follows the surface of the shell of a heatexchanger into which heat exchanger baffle 2700 is installed. Continuousperimeter 2702 is configured such that it surrounds all of the tubes ofthe heat exchanger within the shell, such as, for example, the entireplurality of tubes 2608 described above and shown in FIGS. 26A and 26B.Continuous perimeter 2702 can be configured to match the inner diameterof the shell, such as shell 2602 described above and shown in FIGS. 26Aand 26B.

Fluid passage 2704 is an opening located within continuous perimeter2702 allowing fluid to flow from one side of the baffle 2700 to theother. Fluid passage 2704 can be within the continuous perimeter 2702such that it is completely surrounded by portions of heat exchangerbaffle 2700 that obstruct fluid flow. In an embodiment, fluid passage2704 has a generally pentagonal shape. In an embodiment, fluid passage2704 has rounded corners. In an embodiment, the perimeter of fluidpassage 2704 includes one or more recesses formed therein correspondingto tubes of the heat exchanger, such as tubes 2608, that would beintersected by the perimeter of the fluid passage 2704. In anembodiment, fluid passage 2704. In an embodiment, the area of fluidpassage 2704 is between at or about 25% and at or about 35% of the areadefined by continuous perimeter 2702. In an embodiment, the area offluid passage 2704 is at or about 30% of the area defined by continuousperimeter 2702.

Channels 2706 each surround one of the tubes of the heat exchanger, suchas tubes 2608 described above and shown in FIGS. 26A and 26B. In anembodiment, the channels are sized such that they contact the tubes 2608and do not provide spaces allowing fluid flow between the exterior ofthe tubes 2608 and the heat exchanger baffle 2700. In an embodiment, thenumber of channels 2706 can be the number of tubes 2608 outside of thefluid passage 2704.

Notches 2708 are formed in continuous perimeter 2702 of heat exchangerbaffle 2700 at positions corresponding to where any longitudinal bafflesare located on an inner surface of the shell. The longitudinal bafflescan be, for example, the longitudinal baffles 2620 described above andshown in FIGS. 26A and 26B. In an embodiment, the notches 2708 formed inthe heat exchanger baffle 2700 can be configured to engage withcorresponding notches formed in the longitudinal baffles.

Where multiple heat exchanger baffles 2700 are included in a suctionline heat exchanger, the fluid passages 2704 of the heat exchangerbaffles 2700 can be offset from one another such that the respectivefluid passages 2704 are not aligned with one another. In an embodiment,the fluid passage 2704 of a heat exchanger baffle 2700 is aligned with aportion of the adjacent heat exchanger baffle that obstructs fluid flow.In an embodiment, the fluid passages 2704 are opposite one another, forexample, having a fluid passage 2704 of a first baffle towards a bottomof the shell and a fluid passage 2704 of a second baffle towards the topof the shell.

Aspects:

Any of aspects 1-8 can be combined with any of aspects 9-13 and any ofaspects 14 and 15, and any of aspects 9-13 may be combined with any ofaspects 14 and 15. It is understood that any of aspects 1-15 can becombined with any other aspects recited herein.

Aspect 1. A refrigerant circuit, comprising:

a compressor;a condenser;an expander;an evaporator; anda suction line heat exchanger configured to exchange heat between aliquid side receiving a working fluid as a liquid leaving the condenser,prior to the expander and a gas side receiving the working fluid as agas leaving the evaporator, prior to the compressor, wherein the liquidside includes a shell and the gas side includes a plurality of tubesextending through the shell, wherein the suction line heat exchanger isconfigured such that a discharge of the compressor has a dischargesuperheat of at or about 3.3° C. or more than 3.3° C.

Aspect 2. The refrigerant circuit according to aspect 1, furthercomprising a throttling valve between the plurality of tubes of thesuction line heat exchanger and the compressor.

Aspect 3. The refrigerant circuit according to any of aspects 1-2,wherein:

the shell has a length of at or about one meter,the shell has a diameter of between at or about 200 millimeters (mm) andat or about 220 mm, the plurality of tubes includes between at or about55 and at or about 65 tubes, andeach of the plurality of tubes has an interior diameter of between at orabout 15 mm and at or about 18 mm.

Aspect 4. The refrigerant circuit according to any of aspects 1-3,wherein a pressure drop across the gas side of the suction line heatexchanger is 10 kPa or less for refrigerant R1234ze.

Aspect 5. The refrigerant circuit according to any of aspects 1-4,wherein a temperature of gas leaving the gas side of the suction lineheat exchanger is greater than 1.5° C. or at or about 1.5° C. greaterthan a temperature of the gas entering the gas side of the suction lineheat exchanger.

Aspect 6. The refrigerant circuit according to any of aspects 1-5,further comprising a plurality of baffles within the shell, wherein eachof the baffles includes a continuous perimeter in contact with an entireinner diameter of the shell and an open area.

Aspect 7. The refrigerant circuit according aspect 6, wherein the openarea comprises at or about 30% of the area defined by the continuousperimeter.

Aspect 8. The refrigerant circuit according to any of aspects 1-7,wherein the shell includes a plurality of longitudinal baffles eachextending a length of the shell and extending from an inner surface ofthe shell to one of the plurality of tubes.

Aspect 9. A suction line heat exchanger comprising:

a liquid side including:

an inlet connected to a condenser of a refrigeration circuit;

an outlet connected to an expander of the refrigeration circuit; and

a shell defining an internal space; and

a gas side including:

an inlet connected to an evaporator of the refrigeration circuit;

an inlet header connecting the inlet to a plurality of tubes, theplurality of tubes extending through the internal space from one end ofthe shell to an opposing end of the shell;

an outlet header connecting the plurality of tubes to an outlet, whereinthe suction line heat exchanger is configured to increase a dischargesuperheat of a compressor of the refrigeration circuit such that thedischarge superheat is at or about 3.3° C. or more than 3.3° C.

Aspect 10. The suction line heat exchanger according to aspect 9,wherein a pressure drop across the gas side is 10 kPa or less forrefrigerant R1234ze.

Aspect 11. The suction line heat exchanger according to any of aspects9-10, wherein there is a chamfer where each of the tubes is connected tothe inlet header, and a chamfer where each of the tubes is connected tothe outlet header.

Aspect 12. The suction line heat exchanger according to any of aspects9-11, further comprising a plurality of baffles within the shell,wherein each of the baffles includes a continuous perimeter in contactwith an entire inner diameter of the shell and an open area, the openarea comprises at or about 30% of the area defined by the continuousperimeter.

Aspect 13. The suction line heat exchanger according to any of aspects9-12, wherein the shell includes a plurality of longitudinal baffleseach extending a length of the shell and extending from an inner surfaceof the shell to one of the plurality of tubes.

Aspect 14. A method of increasing superheat of a refrigerant,comprising: directing relatively hot liquid refrigerant from a condenserto a suction line heat exchanger; directing relatively cool gaseousrefrigerant from an evaporator to the suction line heat exchanger;performing heat exchange between the relatively hot liquid refrigerantand the relatively cool gaseous refrigerant using the suction line heatexchanger, to increase the heat of the relatively cool gaseousrefrigerant to obtain a heated gaseous refrigerant; and directing theheated gaseous refrigerant to a suction port of the compressor, whereinthe compressor heats and pressurizes the heated gaseous refrigerant toobtain a superheated gaseous refrigerant.

Aspect 15. The method of aspect 14, wherein the refrigerant is R1234ze.

The terminology used in this specification is intended to describeparticular embodiments and is not intended to be limiting. The terms“a,” “an,” and “the” include the plural forms as well, unless clearlyindicated otherwise. The terms “comprises” and/or “comprising,” whenused in this specification, specify the presence of the stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, and/or components.

With regard to the preceding description, it is to be understood thatchanges may be made in detail, especially in matters of the constructionmaterials employed and the shape, size, and arrangement of parts withoutdeparting from the scope of the present disclosure. This specificationand the embodiments described are exemplary only, with the true scopeand spirit of the disclosure being indicated by the claims that follow.

1. A heat transfer circuit, comprising: a compressor for compressing aworking fluid; a condenser for cooling the working fluid; an expansiondevice for expanding the working fluid; an evaporator for providing afirst heating of the working fluid flowing through the evaporator, thefirst heating being a heat exchange between the working fluid and aprocess fluid flowing through the evaporator, a flow path of the workingfluid extending from the compressor through the condenser, the expansiondevice, the evaporator, and back to the compressor, the flow pathincluding a suction stream disposed after the first heating and beforethe compressor; and a heat source, the suction stream including the heatsource and the heat source configured to provide a second heating of theworking fluid.
 2. The heat transfer circuit of claim 1, wherein the heatsource is disposed within the evaporator.
 3. The heat transfer circuitof claim 2, wherein the heat source is an electric heater.
 4. The heattransfer circuit of claim 2, wherein the evaporator includes a first setof heat exchanger tubes through which the process fluid flows, and theworking fluid flowing past the first set of tubes undergoing the firstheating, and the heat source is a second set of heat exchanger tubes inthe evaporator, the second heating of the working fluid being a heatexchange between the working fluid flowing past the second set of heatexchange tubes and a third fluid flowing through the second set of heatexchanger tubes.
 5. The heat transfer circuit of claim 4, wherein thethird fluid is a portion of the compressed working fluid discharged bythe compressor before the compressed working fluid flows through theexpansion device.
 6. The heat transfer circuit of claim 4, wherein thethird fluid is the same type of fluid as the process fluid.
 7. The heattransfer circuit of claim 4, wherein a second process fluid flowsthrough the condenser and absorbs heat from the working fluid to providethe cooling of the working fluid, and the third fluid includes a portionof the second process fluid.
 8. The heat transfer circuit of claim 1,the heat source is disposed in the suction stream between the evaporatorand the compressor.
 9. The heat transfer circuit of claim 8, wherein theheat source is an electric heater.
 10. The heat transfer circuit ofclaim 8, wherein the heat source is a heat exchanger including a firstside and a second side, the working fluid heated by the heat sourceflowing through the first side, a third fluid flowing through the secondside, and the second heating of the working fluid being a heat exchangebetween the third fluid and the working fluid.
 11. The heat transfercircuit of claim 10, wherein the third fluid is a portion of thecompressed working fluid discharged by the compressor before thecompressed working fluid flows through the expansion device.
 12. Theheat transfer circuit of claim 10, wherein the third fluid is the sametype of fluid as the process fluid.
 13. The heat transfer circuit ofclaim 10, wherein a second process fluid flows through the condenser andabsorbs heat from the working fluid to provide the cooling of theworking fluid, and the third fluid includes a portion of the secondprocess fluid.
 14. The heat transfer circuit of claim 8, furthercomprising: a suction pipe extending to a suction inlet of thecompressor, the suction stream including the suction pipe, wherein theheat source extends along an outside of the suction pipe.
 15. The heattransfer circuit of claim 1, further comprising: a controller configuredto control heat provided by the heat source to the working fluid basedon a suction temperature of the working fluid entering the compressor.16. The heat transfer circuit of claim 1, wherein the heat source isconfigured to increase superheat of the working fluid entering a suctioninlet of the compressor.
 17. A method of operating a heat transfercircuit, the heat transfer circuit including a compressor, a condenser,an expansion device, an evaporator, a heat source, and a working fluidflowing through the heat transfer circuit, the method comprising:compressing the working fluid with the compressor; cooling the workingfluid compressed by the compressor with the condenser; expanding theworking fluid cooled by the condenser with the expansion device; heatingthe working fluid expanded by the expansion device in the evaporatorwith a process fluid, the working fluid absorbing heat from the processfluid; and heating the working fluid heated by the process fluid withthe heat source, the working fluid heated with the heat source as theworking fluid flows through a suction stream, the suction streamincluding the heat source and disposed after a location at which theworking fluid is heated by the process fluid and before the compressor.18. The method of claim 17, wherein heating the working fluid with theheat source includes heating the working fluid flowing from theevaporator to the compressor.
 19. The method of claim 17, whereinheating the working fluid with the heat source includes increasingsuperheat of the working fluid entering a suction inlet of thecompressor.
 20. The method of claim 17, further comprising: directingthe working fluid from an inlet of the evaporator, past a first set ofheat exchanger tubes in the evaporator through which the first fluidflows, past the heat source, and to an outlet of the evaporator in thisorder, wherein the suction stream includes a portion of the evaporatorlocated after the first set of heat exchanger tubes.
 21. The method ofclaim 17, further comprising: directing at least a portion of thecompressed working fluid discharged by the compressor, which has notbeen expanded by the expansion device, through a first side of the heatsource, wherein heating the working fluid heated by the process fluidwith the heat source includes directing the working fluid heated by theheat source through a second side of the heat source. 22-41. (canceled)